My Network Lab: Manipulating BGP Local Preference and MED

The BGP Local Preference (Local_Pref) PA gives the routers inside a single AS a value that they can set per-route and advertise to all iBGP routers inside the AS, so that all routers in the AS agree about which router is the best exit point for packets destined for that prefix. By design, Local_Pref can be set by routers as they receive eBGP routes by using an inbound route map. The routers then advertise the Local_Pref in iBGP updates. As a result, all the routers in the same AS can then make the same choice of which route is best, agreeing as to which router to use to exit the AS for each prefix.

To set the Local_Pref, a router can use the neighbor <neighbor-ip> route-map in BGP subcommand. Typically, a router uses this command with the inbound direction for routes received from eBGP peers. Then, with no additional configuration required, the router then advertises the Local_Pref to any iBGP peers.

With a dual-homed design, at least two links exist between an enterprise and its ISP. The enterprise can announce to the ISP a value Multi-Exit Discriminator (MED) that tells the ISP which path into the enterprise is best. As a result, the ISP can discriminate between the multiple exit points
from that ISP to the enterprise. Because MED lets the enterprise ASN tell just the neighboring ASN which link into the enterprise to use, engineers typically use MED when advertising an enterprise’s public IP address space. Those inbound routes into the enterprise from the ISP typically consist of
either one, or a few, public IP address ranges.

MED configuration usually occurs on the routers in the AS that want to control inbound routes from the neighboring AS. The show ip bgp command output refer to MED as metric. Note that the route map uses the set metric command, rather than set med (which does not exist). The output for the show ip bgp command, the output lists MED under the heading metric. Specifically, note that
even the show ip route command lists the MED value in brackets as the metric for the BGP route.

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface loop 0

R1(config-if)#

*Jul 17 09:42:44.487: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up

R1(config-if)#ip address 192.168.100.1 255.255.255.0

R1(config-if)#

R1(config-if)#interface serial 2/0

R1(config-if)#ip address 192.168.1.5 255.255.255.252

R1(config-if)#no shut

R1(config-if)#

*Jul 17 09:43:48.511: %LINK-3-UPDOWN: Interface Serial2/0, changed state to up

R1(config-if)#

*Jul 17 09:43:49.519: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to up

R1(config-if)#

R1(config-if)#interface serial 2/2

R1(config-if)#ip address 192.168.1.1 255.255.255.252

R1(config-if)#no shut

R1(config-if)#

*Jul 17 09:44:16.047: %LINK-3-UPDOWN: Interface Serial2/2, changed state to up

R1(config-if)#

*Jul 17 09:44:16.851: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to down

*Jul 17 09:44:17.055: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/2, changed state to up

R1(config-if)#end

R1#

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#interface loop 0

R2(config-if)#

*Jul 17 09:45:16.487: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up

R2(config-if)#ip addres 172.16.64.1 255.255.255.0

R2(config-if)#

R2(config-if)#interface serial 2/0

R2(config-if)#ip address 192.168.1.6 255.255.255.252

R2(config-if)#no shut

R2(config-if)#

*Jul 17 09:45:53.903: %LINK-3-UPDOWN: Interface Serial2/0, changed state to up

R2(config-if)#

*Jul 17 09:45:54.911: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to up

R2(config-if)#

R2(config-if)#do ping 192.168.1.5

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.5, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/20/28 ms

R2(config-if)#

R2(config-if)#interface serial 2/1

R2(config-if)#ip address 172.16.1.1 255.255.255.0

R2(config-if)#no shut

R2(config-if)#

*Jul 17 09:46:43.211: %LINK-3-UPDOWN: Interface Serial2/1, changed state to up

R2(config-if)#

*Jul 17 09:46:44.219: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/1, changed state to up

R2(config-if)#end

R2#

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#interface loop 0

R3(config-if)#

*Jul 17 09:47:17.131: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up

R3(config-if)#ip address 172.16.32.1 255.255.255.0

R3(config-if)#

R3(config-if)#interface serial 2/1

R3(config-if)#ip address 172.16.1.2 255.255.255.0

R3(config-if)#no shut

R3(config-if)#

*Jul 17 09:47:55.323: %LINK-3-UPDOWN: Interface Serial2/1, changed state to up

R3(config-if)#

*Jul 17 09:47:56.331: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/1, changed state to up

R3(config-if)#

R3(config-if)#do ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/23/36 ms

R3(config-if)#

R3(config-if)#interface serial 2/2

R3(config-if)#ip address 192.168.1.2 255.255.255.252

R3(config-if)#no shut

R3(config-if)#

*Jul 17 09:48:25.555: %LINK-3-UPDOWN: Interface Serial2/2, changed state to up

R3(config-if)#

*Jul 17 09:48:26.563: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/2, changed state to up

R3(config-if)#

R3(config-if)#do ping 192.168.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:

.!!!!

Success rate is 80 percent (4/5), round-trip min/avg/max = 16/25/36 ms

R3(config-if)#

R3(config-if)#end

R3#

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#router eigrp 1 // IOS 15 DEFAULTS TO EIGRP no auto-summary

R2(config-router)#network 172.16.0.0

R2(config-router)#end

R2#

*Jul 17 09:50:32.627: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 172.16.1.2 (Serial2/1) is up: new adjacency

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#router eigrp 1

R3(config-router)#network 172.16.0.0

R3(config-router)#

*Jul 17 09:50:32.999: %DUAL-5-NBRCHANGE: EIGRP-IPv4 1: Neighbor 172.16.1.1 (Serial2/1) is up: new adjacency

R3(config-router)#end

R3#

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#router bgp 64512

R2(config-router)#neighbor 172.16.32.1 remote-as 64512 // CONFIGURE IBGP PEER

R2(config-router)#neighbor 172.16.32.1 update-source loop 0 // CONFIGURE IF MULTIPLE PATHS EXIST

R2(config-router)#end

R2#

*Jul 17 09:53:09.299: %BGP-5-ADJCHANGE: neighbor 172.16.32.1 Up

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#router bgp 64512

R3(config-router)#neighbor 172.16.64.1 remote-as 64512

R3(config-router)#neighbor 172.16.64.1 update-source loop 0

*Jul 17 09:53:09.667: %BGP-5-ADJCHANGE: neighbor 172.16.64.1 Up

R3(config-router)#end

R3#

R3#show ip bgp neighbors

BGP neighbor is 172.16.64.1, remote AS 64512, internal link // NOTICE internal link FOR IBGP

BGP version 4, remote router ID 172.16.64.1

BGP state = Established, up for 00:01:52

Last read 00:00:07, last write 00:00:06, hold time is 180, keepalive interval is 60 seconds

Neighbor sessions:

1 active, is not multisession capable (disabled)

Neighbor capabilities:

Route refresh: advertised and received(new)

Four-octets ASN Capability: advertised and received

Address family IPv4 Unicast: advertised and received

Enhanced Refresh Capability: advertised and received

Multisession Capability:

Stateful switchover support enabled: NO for session 1

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 1 1

Keepalives: 4 4

Route Refresh: 0 0

Total: 6 6

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

Session: 172.16.64.1

BGP table version 1, neighbor version 1/0

Output queue size : 0

Index 1, Advertise bit 0

1 update-group member

Slow-peer detection is disabled

Slow-peer split-update-group dynamic is disabled

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 0 0

Prefixes Total: 0 0

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 0

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Total: 0 0

Number of NLRIs in the update sent: max 0, min 0

Last detected as dynamic slow peer: never

Dynamic slow peer recovered: never

Refresh Epoch: 1

Last Sent Refresh Start-of-rib: never

Last Sent Refresh End-of-rib: never

Last Received Refresh Start-of-rib: never

Last Received Refresh End-of-rib: never

Sent Rcvd

Refresh activity: ---- ----

Refresh Start-of-RIB 0 0

Refresh End-of-RIB 0 0

Address tracking is enabled, the RIB does have a route to 172.16.64.1

Connections established 1; dropped 0

Last reset never

Transport(tcp) path-mtu-discovery is enabled

Graceful-Restart is disabled

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 255

Local host: 172.16.32.1, Local port: 179

Foreign host: 172.16.64.1, Foreign port: 30331

Connection tableid (VRF): 0

Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0xDB824):

Timer Starts Wakeups Next

Retrans 5 0 0x0

TimeWait 0 0 0x0

AckHold 5 2 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

Linger 0 0 0x0

ProcessQ 0 0 0x0

iss: 512159364 snduna: 512159521 sndnxt: 512159521

irs: 2436045535 rcvnxt: 2436045692

sndwnd: 16228 scale: 0 maxrcvwnd: 16384

rcvwnd: 16228 scale: 0 delrcvwnd: 156

SRTT: 487 ms, RTTO: 3168 ms, RTV: 2681 ms, KRTT: 0 ms

minRTT: 12 ms, maxRTT: 1000 ms, ACK hold: 200 ms

Status Flags: passive open, gen tcbs

Option Flags: nagle, path mtu capable

IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):

Rcvd: 12 (out of order: 0), with data: 6, total data bytes: 156

Sent: 11 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 6, total data bytes: 156

Packets received in fast path: 0, fast processed: 0, slow path: 0

fast lock acquisition failures: 0, slow path: 0

TCP Semaphore 0x6A3CA688 FREE

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router bgp 200

R1(config-router)#neighbor 192.168.1.6 remote-as 64512 // CONFIGURE EBGP PEER

R1(config-router)#neighbor 192.168.1.2 remote-as 64512 // NO NEED FOR update-source SINCE EBGP ARE COMMONLY POINT-TO-POINT LINKS (DIRECTLY CONNECTED)

R1(config-router)#network 192.168.100.0

R1(config-router)#end

R1#

*Jul 17 09:58:48.955: %BGP-5-ADJCHANGE: neighbor 192.168.1.6 Up

R1#

*Jul 17 10:03:49.043: %BGP-5-ADJCHANGE: neighbor 192.168.1.2 Up

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#ip route 172.16.0.0 255.255.0.0 null0

R2(config)#

R2(config)#router bgp 64512

R2(config-router)#neighbor 192.168.1.5 remote-as 200

R2(config-router)#

*Jul 17 09:58:48.855: %BGP-5-ADJCHANGE: neighbor 192.168.1.5 Up

R2(config-router)#

R2(config-router)#network 172.16.0.0

R2(config-router)#end

R2#

*Jul 17 09:59:02.679: %SYS-5-CONFIG_I: Configured from console by console

R2#

R2#show ip bgp neighbors

BGP neighbor is 172.16.32.1, remote AS 64512, internal link

BGP version 4, remote router ID 172.16.32.1

BGP state = Established, up for 00:06:02

Last read 00:00:42, last write 00:00:13, hold time is 180, keepalive interval is 60 seconds

Neighbor sessions:

1 active, is not multisession capable (disabled)

Neighbor capabilities:

Route refresh: advertised and received(new)

Four-octets ASN Capability: advertised and received

Address family IPv4 Unicast: advertised and received

Enhanced Refresh Capability: advertised and received

Multisession Capability:

Stateful switchover support enabled: NO for session 1

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 3 1

Keepalives: 8 8

Route Refresh: 0 0

Total: 12 10

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

Session: 172.16.32.1

BGP table version 3, neighbor version 3/0

Output queue size : 0

Index 1, Advertise bit 0

1 update-group member

Slow-peer detection is disabled

Slow-peer split-update-group dynamic is disabled

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 2 0

Prefixes Total: 2 0

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 0

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Total: 0 0

Number of NLRIs in the update sent: max 1, min 0

Last detected as dynamic slow peer: never

Dynamic slow peer recovered: never

Refresh Epoch: 1

Last Sent Refresh Start-of-rib: never

Last Sent Refresh End-of-rib: never

Last Received Refresh Start-of-rib: never

Last Received Refresh End-of-rib: never

Sent Rcvd

Refresh activity: ---- ----

Refresh Start-of-RIB 0 0

Refresh End-of-RIB 0 0

Address tracking is enabled, the RIB does have a route to 172.16.32.1

Connections established 1; dropped 0

Last reset never

Transport(tcp) path-mtu-discovery is enabled

Graceful-Restart is disabled

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 255

Local host: 172.16.64.1, Local port: 30331

Foreign host: 172.16.32.1, Foreign port: 179

Connection tableid (VRF): 0

Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x119AF0):

Timer Starts Wakeups Next

Retrans 12 0 0x0

TimeWait 0 0 0x0

AckHold 9 6 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 1 0 0x153AF8

DeadWait 0 0 0x0

Linger 0 0 0x0

ProcessQ 0 0 0x0

iss: 2436045535 snduna: 2436045883 sndnxt: 2436045883

irs: 512159364 rcvnxt: 512159597

sndwnd: 16037 scale: 0 maxrcvwnd: 16384

rcvwnd: 16152 scale: 0 delrcvwnd: 232

SRTT: 798 ms, RTTO: 2221 ms, RTV: 1423 ms, KRTT: 0 ms

minRTT: 12 ms, maxRTT: 1000 ms, ACK hold: 200 ms

Status Flags: active open

Option Flags: nagle, path mtu capable

IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):

Rcvd: 21 (out of order: 0), with data: 10, total data bytes: 232

Sent: 22 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 12, total data bytes: 347

Packets received in fast path: 0, fast processed: 0, slow path: 0

fast lock acquisition failures: 0, slow path: 0

TCP Semaphore 0x6A3B5468 FREE

BGP neighbor is 192.168.1.5, remote AS 200, external link // NOTICE external link FOR EBGP

BGP version 4, remote router ID 192.168.100.1

BGP state = Established, up for 00:00:22

Last read 00:00:22, last write 00:00:22, hold time is 180, keepalive interval is 60 seconds

Neighbor sessions:

1 active, is not multisession capable (disabled)

Neighbor capabilities:

Route refresh: advertised and received(new)

Four-octets ASN Capability: advertised and received

Address family IPv4 Unicast: advertised and received

Enhanced Refresh Capability: advertised and received

Multisession Capability:

Stateful switchover support enabled: NO for session 1

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 1 2

Keepalives: 2 2

Route Refresh: 0 0

Total: 4 5

Default minimum time between advertisement runs is 30 seconds

For address family: IPv4 Unicast

Session: 192.168.1.5

BGP table version 3, neighbor version 2/3

Output queue size : 0

Index 2, Advertise bit 1

2 update-group member

Slow-peer detection is disabled

Slow-peer split-update-group dynamic is disabled

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 0 1 (Consumes 64 bytes)

Prefixes Total: 0 1

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 1

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Bestpath from this peer: 1 n/a

Total: 1 0

Number of NLRIs in the update sent: max 0, min 0

Last detected as dynamic slow peer: never

Dynamic slow peer recovered: never

Refresh Epoch: 1

Last Sent Refresh Start-of-rib: never

Last Sent Refresh End-of-rib: never

Last Received Refresh Start-of-rib: never

Last Received Refresh End-of-rib: never

Sent Rcvd

Refresh activity: ---- ----

Refresh Start-of-RIB 0 0

Refresh End-of-RIB 0 0

Address tracking is enabled, the RIB does have a route to 192.168.1.5

Connections established 1; dropped 0

Last reset never

Transport(tcp) path-mtu-discovery is enabled

Graceful-Restart is disabled

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 1

Local host: 192.168.1.6, Local port: 179

Foreign host: 192.168.1.5, Foreign port: 61203

Connection tableid (VRF): 0

Maximum output segment queue size: 50

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x119AF8):

Timer Starts Wakeups Next

Retrans 3 0 0x0

TimeWait 0 0 0x0

AckHold 3 0 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

Linger 0 0 0x0

ProcessQ 0 0 0x0

iss: 3505144302 snduna: 3505144421 sndnxt: 3505144421

irs: 52768916 rcvnxt: 52769089

sndwnd: 16266 scale: 0 maxrcvwnd: 16384

rcvwnd: 16212 scale: 0 delrcvwnd: 172

SRTT: 330 ms, RTTO: 3159 ms, RTV: 2829 ms, KRTT: 0 ms

minRTT: 12 ms, maxRTT: 1000 ms, ACK hold: 200 ms

Status Flags: passive open, gen tcbs

Option Flags: nagle, path mtu capable

IP Precedence value : 6

Datagrams (max data segment is 1460 bytes):

Rcvd: 8 (out of order: 0), with data: 4, total data bytes: 172

Sent: 7 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 4, total data bytes: 118

Packets received in fast path: 0, fast processed: 0, slow path: 0

fast lock acquisition failures: 0, slow path: 0

TCP Semaphore 0x6A3B5388 FREE

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#ip route 172.16.0.0 255.255.0.0 null0

R3(config)#router bgp 64512

R3(config-router)#neighbor 192.168.1.1 remote-as 200

R3(config-router)#network 172.16.0.0

R3(config-router)#

*Jul 17 10:03:49.279: %BGP-5-ADJCHANGE: neighbor 192.168.1.1 Up

R3(config-router)#end

R3#

*Jul 17 10:04:01.287: %SYS-5-CONFIG_I: Configured from console by console

R3#

R3#show ip bgp ?

A.B.C.D Network in the BGP routing table to display

A.B.C.D/nn IP prefix <network>/<length>, e.g., 35.0.0.0/8

all All address families

cidr-only Display only routes with non-natural netmasks

community Display routes matching the communities

community-list Display routes matching the community-list

dampening Display detailed information about dampening

extcommunity-list Display routes matching the extcommunity-list

filter-list Display routes conforming to the filter-list

import Display route topology import / export activity

inconsistency Display all inconsistent paths

inconsistent-as Display only routes with inconsistent origin ASs

injected-paths Display all injected paths

ipv4 Address family

ipv6 Address family

l2vpn Address family

labels Display Labels for IPv4 NLRI specific information

neighbors Detailed information on TCP and BGP neighbor connections

nexthops Nexthop address table

nsap Address family

oer-paths Display all oer controlled paths

paths Path information

peer-group Display information on peer-groups

pending-prefixes Display prefixes pending deletion

prefix-list Display routes matching the prefix-list

quote-regexp Display routes matching the AS path "regular expression"

regexp Display routes matching the AS path regular expression

replication Display replication status of update-group(s)

rib-failure Display bgp routes that failed to install in the routing

table (RIB)

route-map Display routes matching the route-map

route-server Route server information

rpki Display RPKI Neighbor Cache

rtfilter Address family

summary Summary of BGP neighbor status

template Display peer-policy/peer-session templates

topology Routing topology instance

update-group Display information on update-groups

update-sources Update source interface table

va Display virtual aggregation prefixes

version Display prefixes with matching version numbers

vpnv4 Address family

vpnv6 Address family

| Output modifiers

<cr>

R3#show ip bgp summary // ALTERNATE COMMAND TO VERIFY BGP NEIGHBOR STATUS

BGP router identifier 172.16.32.1, local AS number 64512

BGP table version is 4, main routing table version 4

2 network entries using 296 bytes of memory

4 path entries using 256 bytes of memory

4/2 BGP path/bestpath attribute entries using 544 bytes of memory

1 BGP AS-PATH entries using 24 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

BGP using 1120 total bytes of memory

BGP activity 2/0 prefixes, 4/0 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

172.16.64.1 4 64512 17 17 4 0 0 00:11:00 2

192.168.1.1 4 200 7 5 2 0 0 00:00:20 1

R1#clear ip bgp ?

* Clear all peers

<1-4294967295> Clear peers with the AS number

<1.0-XX.YY> Clear peers with the AS number

A.B.C.D BGP neighbor address to clear

X:X:X:X::X BGP neighbor address to clear

all All address families

dampening Clear route flap dampening information

external Clear all external peers

flap-statistics Clear route flap statistics

internal Clear BGP internal statistics counters

ipv4 Address family

ipv6 Address family

l2vpn Address family

nsap Address family

peer-group Clear all members of peer-group

rtfilter Address family

sso SSO related

table-map Update BGP table-map configuration

topology Routing topology instance

update-group Clear all members of update-group

vpnv4 Address family

vpnv6 Address family

R1#clear ip bgp *

R1#

*Jul 17 10:05:46.763: %BGP-5-ADJCHANGE: neighbor 192.168.1.2 Down User reset

*Jul 17 10:05:46.767: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.2 IPv4 Unicast topology base removed from session User reset

*Jul 17 10:05:46.771: %BGP-5-ADJCHANGE: neighbor 192.168.1.6 Down User reset

*Jul 17 10:05:46.775: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.6 IPv4 Unicast topology base removed from session User reset

R1#

*Jul 17 10:05:47.851: %BGP-5-ADJCHANGE: neighbor 192.168.1.6 Up

*Jul 17 10:05:47.851: %BGP-5-ADJCHANGE: neighbor 192.168.1.2 Up

R1#

R1#ping 172.16.64.1 // R2 DON'T HAVE RETURN PATH TO R1 SOURCE IP 192.168.1.5

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.64.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

R1#

R1#ping 172.16.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

R1#

R1#ping 172.16.32.1 // PING IS OK SINCE BEST PATH IS VIA R3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.32.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/19/24 ms

R1#

R1#ping 172.16.1.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/16/20 ms

R1#show ip bgp // BEST PATH TO 172.16.0.0/16 IS VIA R3

BGP table version is 3, local router ID is 192.168.100.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* 172.16.0.0 192.168.1.6 0 0 64512 i

*> 192.168.1.2 0 0 64512 i

*> 192.168.100.0 0.0.0.0 0 32768 i

R1#ping 172.16.1.1 source 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.1, timeout is 2 seconds:

Packet sent with a source address of 192.168.100.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/15/28 ms

R1#

R1#ping 172.16.32.1 source 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.32.1, timeout is 2 seconds:

Packet sent with a source address of 192.168.100.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/19/24 ms

R1#

R1#ping 172.16.1.2 source 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.1.2, timeout is 2 seconds:

Packet sent with a source address of 192.168.100.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/19/24 ms

R1#

R1#ping 172.16.64.1 source 192.168.100.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.64.1, timeout is 2 seconds:

Packet sent with a source address of 192.168.100.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/20/28 ms

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router bgp 200

R1(config-router)#network 192.168.1.0 mask 255.255.255.252 // R2 AND R3 DON'T KNOW EACH OTHERS EBGP PEERING LINKS

R1(config-router)#network 192.168.1.4 mask 255.255.255.252

R1(config-router)#end

R1#

*Jul 17 10:12:47.475: %SYS-5-CONFIG_I: Configured from console by console

R1#

R1#show ip bgp // R1 (ISP) INJECTS /30 WAN LINKS TO R2 AND R3

BGP table version is 5, local router ID is 192.168.100.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* 172.16.0.0 192.168.1.6 0 0 64512 i

*> 192.168.1.2 0 0 64512 i

*> 192.168.1.0/30 0.0.0.0 0 32768 i

*> 192.168.1.4/30 0.0.0.0 0 32768 i

*> 192.168.100.0 0.0.0.0 0 32768 i

R2#show ip bgp

BGP table version is 7, local router ID is 172.16.64.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.32.1 0 100 0 i

*> 0.0.0.0 0 32768 i

* i 192.168.1.0/30 192.168.1.1 0 100 0 200 i

*> 192.168.1.5 0 0 200 i

r i 192.168.1.4/30 192.168.1.1 0 100 0 200 i

r> 192.168.1.5 0 0 200 i

* i 192.168.100.0 192.168.1.1 0 100 0 200 i

*> 192.168.1.5 0 0 200 i

R3#show ip bgp

BGP table version is 8, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 172.16.0.0 0.0.0.0 0 32768 i

* i 172.16.64.1 0 100 0 i

r i 192.168.1.0/30 192.168.1.5 0 100 0 200 i

r> 192.168.1.1 0 0 200 i

* i 192.168.1.4/30 192.168.1.5 0 100 0 200 i

*> 192.168.1.1 0 0 200 i

* i 192.168.100.0 192.168.1.5 0 100 0 200 i

*> 192.168.1.1 0 0 200 i

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router bgp 200

R1(config-router)#no network 192.168.1.0 mask 255.255.255.252 // NOT ALWAYS DESIRABLE FOR ISP TO ADVERTISE EBGP WAN LINKS

R1(config-router)#no network 192.168.1.4 mask 255.255.255.252

R1(config-router)#exit

R1(config)#interface serial 2/2

R1(config-if)#shut

R1(config-if)#

*Jul 17 10:17:57.303: %BGP-5-ADJCHANGE: neighbor 192.168.1.2 Down Interface flap

*Jul 17 10:17:57.303: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.2 IPv4 Unicast topology base removed from session Interface flap

R1(config-if)#

*Jul 17 10:17:59.267: %LINK-5-CHANGED: Interface Serial2/2, changed state to administratively down

*Jul 17 10:18:00.267: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/2, changed state to down

R3#

*Jul 17 10:18:30.071: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/2, changed state to down

*Jul 17 10:18:30.103: %BGP-5-ADJCHANGE: neighbor 192.168.1.1 Down Interface flap

*Jul 17 10:18:30.103: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.1 IPv4 Unicast topology base removed from session Interface flap

R3#

R3#show ip bgp // EBGP NEXT HOP IS CARRIED IN IBGP UNCHANGED

BGP table version is 13, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 172.16.0.0 0.0.0.0 0 32768 i

* i 172.16.64.1 0 100 0 i

* i 192.168.100.0 192.168.1.5 0 100 0 200 i

R3#

R3#show ip route // R3 DOESN'T HAVE 192.168.100/24 (VIA 192.168.1.5) IN ITS ROUTING TABLE

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.2/32 is directly connected, Serial2/1

C 172.16.32.0/24 is directly connected, Loopback0

L 172.16.32.1/32 is directly connected, Loopback0

D 172.16.64.0/24 [90/2297856] via 172.16.1.1, 00:28:16, Serial2/1

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#router bgp 64512

R2(config-router)#neighbor 172.16.32.1 next-hop-self // ADVERTISE IBGP PEER AS NEXT HOP ROUTER FOR EXTERNAL ROUTES

R2(config-router)#end

R2#

*Jul 17 10:21:24.611: %SYS-5-CONFIG_I: Configured from console by console

R2#

*Jul 17 10:21:55.551: %BGP-5-ADJCHANGE: neighbor 172.16.32.1 Down Peer closed the session

*Jul 17 10:21:55.555: %BGP_SESSION-5-ADJCHANGE: neighbor 172.16.32.1 IPv4 Unicast topology base removed from session Peer closed the session

R2#c

*Jul 17 10:21:56.635: %BGP-5-ADJCHANGE: neighbor 172.16.32.1 Up

R2#

R2#clear ip bgp * // FOR NEW BGP POLICY TO TAKE EFFECT (NON-DISRUPTIVE)

R2#

*Jul 17 10:22:01.127: %BGP-5-ADJCHANGE: neighbor 172.16.32.1 Down User reset

*Jul 17 10:22:01.131: %BGP_SESSION-5-ADJCHANGE: neighbor 172.16.32.1 IPv4 Unicast topology base removed from session User reset

*Jul 17 10:22:01.135: %BGP-5-ADJCHANGE: neighbor 192.168.1.5 Down User reset

*Jul 17 10:22:01.139: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.5 IPv4 Unicast topology base removed from session User reset

*Jul 17 10:22:01.963: %BGP-5-ADJCHANGE: neighbor 172.16.32.1 Up

*Jul 17 10:22:01.979: %BGP-5-ADJCHANGE: neighbor 192.168.1.5 Up

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#router bgp 64512

R3(config-router)#neighbor 172.16.64.1 next-hop-self

R3(config-router)#end

R3#

*Jul 17 10:21:50.231: %SYS-5-CONFIG_I: Configured from console by console

R3#clear ip bgp *

R3#

*Jul 17 10:21:55.907: %BGP-5-ADJCHANGE: neighbor 172.16.64.1 Down User reset

*Jul 17 10:21:55.911: %BGP_SESSION-5-ADJCHANGE: neighbor 172.16.64.1 IPv4 Unicast topology base removed from session User reset

R3#

*Jul 17 10:21:56.995: %BGP-5-ADJCHANGE: neighbor 172.16.64.1 Up

R3#

*Jul 17 10:22:01.555: %BGP-5-ADJCHANGE: neighbor 172.16.64.1 Down Peer closed the session

*Jul 17 10:22:01.555: %BGP_SESSION-5-ADJCHANGE: neighbor 172.16.64.1 IPv4 Unicast topology base removed from session Peer closed the session

*Jul 17 10:22:02.335: %BGP-5-ADJCHANGE: neighbor 172.16.64.1 Up

R3#show ip bgp

BGP table version is 3, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.64.1 0 100 0 i

*> 0.0.0.0 0 32768 i

*>i 192.168.100.0 172.16.64.1 0 100 0 200 i

R3#

R3#show ip route // 192.168.100.0/24 IS DISPLAYED IN ROUTING TABLE SINCE R3 KNOWS HOW TO REACH 172.16.64.1 (R2)

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.2/32 is directly connected, Serial2/1

C 172.16.32.0/24 is directly connected, Loopback0

L 172.16.32.1/32 is directly connected, Loopback0

D 172.16.64.0/24 [90/2297856] via 172.16.1.1, 00:33:01, Serial2/1

B 192.168.100.0/24 [200/0] via 172.16.64.1, 00:00:26

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface serial 2/2

R1(config-if)#no shut

R1(config-if)#

*Jul 17 10:24:15.635: %LINK-3-UPDOWN: Interface Serial2/2, changed state to up

R1(config-if)#

*Jul 17 10:24:16.643: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/2, changed state to up

R1(config-if)#

*Jul 17 10:24:21.087: %BGP-5-ADJCHANGE: neighbor 192.168.1.2 Up

R3#

*Jul 17 10:24:21.367: %BGP-5-ADJCHANGE: neighbor 192.168.1.1 Up

R3#

R3#show ip route // R3 DYNAMICALLY LEARNS 192.168.100.0/24 ROUTE VIA R1 EBGP PEER

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.2/32 is directly connected, Serial2/1

C 172.16.32.0/24 is directly connected, Loopback0

L 172.16.32.1/32 is directly connected, Loopback0

D 172.16.64.0/24 [90/2297856] via 172.16.1.1, 00:34:18, Serial2/1

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/30 is directly connected, Serial2/2

L 192.168.1.2/32 is directly connected, Serial2/2

B 192.168.100.0/24 [20/0] via 192.168.1.1, 00:00:30

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#route-map PRIMARY_IN permit 10

R2(config-route-map)#set ?

as-path Prepend string for a BGP AS-path attribute

automatic-tag Automatically compute TAG value

clns OSI summary address

comm-list set BGP community list (for deletion)

community BGP community attribute

dampening Set BGP route flap dampening parameters

default Set default information

extcomm-list Set BGP/VPN extended community list (for deletion)

extcommunity BGP extended community attribute

global Set to global routing table

interface Output interface

ip IP specific information

ipv6 IPv6 specific information

level Where to import route

local-preference BGP local preference path attribute

metric Metric value for destination routing protocol

metric-type Type of metric for destination routing protocol

mpls-label Set MPLS label for prefix

origin BGP origin code

tag Tag value for destination routing protocol

traffic-index BGP traffic classification number for accounting

vrf Define VRF name

weight BGP weight for routing table

R2(config-route-map)#set local-preference ?

<0-4294967295> Preference value

R2(config-route-map)#set local-preference 150 // LOCAL PREF ATTRIBUTE TO MANIPULATE OUTBOUND TRAFFIC FROM AS; SHARED BETWEEN IBGP NEIGHBORS; HIGHER IS PREFERRED

R2(config-route-map)#exit

R2(config)#router bgp 64512

R2(config-router)#neighbor 192.168.1.5 ?

activate Enable the Address Family for this Neighbor

advertise Advertise to this neighbor

advertise-map specify route-map for conditional advertisement

advertisement-interval Minimum interval between sending BGP routing updates

allowas-in Accept as-path with my AS present in it

capability Advertise capability to the peer

default-originate Originate default route to this neighbor

description Neighbor specific description

disable-connected-check one-hop away EBGP peer using loopback address

distribute-list Filter updates to/from this neighbor

dmzlink-bw Propagate the DMZ link bandwidth

ebgp-multihop Allow EBGP neighbors not on directly connected

networks

fall-over session fall on peer route lost

filter-list Establish BGP filters

ha-mode high availability mode

inherit Inherit a template

local-as Specify a local-as number

maximum-prefix Maximum number of prefixes accepted from this peer

next-hop-self Disable the next hop calculation for this neighbor

next-hop-unchanged Propagate next hop unchanged for iBGP paths to this

neighbor

password Set a password

peer-group Member of the peer-group

prefix-list Filter updates to/from this neighbor

remote-as Specify a BGP neighbor

remove-private-as Remove private AS number from outbound updates

route-map Apply route map to neighbor

route-reflector-client Configure a neighbor as Route Reflector client

route-server-client Configure a neighbor as Route Server client

send-community Send Community attribute to this neighbor

send-label Send NLRI + MPLS Label to this peer

shutdown Administratively shut down this neighbor

slow-peer Configure slow-peer

soft-reconfiguration Per neighbor soft reconfiguration

soo Site-of-Origin extended community

timers BGP per neighbor timers

translate-update Translate Update to MBGP format

transport Transport options

ttl-security BGP ttl security check

unsuppress-map Route-map to selectively unsuppress suppressed

routes

update-source Source of routing updates

version Set the BGP version to match a neighbor

weight Set default weight for routes from this neighbor

R2(config-router)#neighbor 192.168.1.5 route-map ?

WORD Name of route map

R2(config-router)#neighbor 192.168.1.5 route-map PRIMARY_IN ?

in Apply map to incoming routes

out Apply map to outbound routes

R2(config-router)#neighbor 192.168.1.5 route-map PRIMARY_IN in

R2(config-router)#end

R2#

*Jul 17 13:29:15.579: %SYS-5-CONFIG_I: Configured from console by console

R2#clear ip bgp * soft

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#route-map SECONDARY_IN permit 10

R3(config-route-map)#set local-preference 125

R3(config-route-map)#exit

R3(config)#router bgp 64512

R3(config-router)#neighbor 192.168.1.1 route-map SECONDARY_IN in

R3(config-router)#end

R3#

*Jul 17 13:29:58.327: %SYS-5-CONFIG_I: Configured from console by console

R3#clear ip bgp * soft

R2#show ip bgp

BGP table version is 4, local router ID is 172.16.64.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.32.1 0 100 0 i

*> 0.0.0.0 0 32768 i

*> 192.168.100.0 192.168.1.5 0 150 0 200 i // PREFER VIA R1 EBGP PEER SINCE HIGHER LOCAL PREF

R3#show ip bgp

BGP table version is 5, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.64.1 0 100 0 i

*> 0.0.0.0 0 32768 i

* 192.168.100.0 192.168.1.1 0 125 0 200 i

*>i 172.16.64.1 0 150 0 200 i // HOP VIA R2 SINCE next-hop-self IS CONFIGURED

R1#show ip bgp // ASYMMETRIC ROUTING IS COMMON IN BGP

BGP table version is 10, local router ID is 192.168.100.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* 172.16.0.0 192.168.1.2 0 0 64512 i

*> 192.168.1.6 0 0 64512 i

*> 192.168.100.0 0.0.0.0 0 32768 i

R1#show ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is not set

B 172.16.0.0/16 [20/0] via 192.168.1.6, 03:11:13

192.168.1.0/24 is variably subnetted, 4 subnets, 2 masks

C 192.168.1.0/30 is directly connected, Serial2/2

L 192.168.1.1/32 is directly connected, Serial2/2

C 192.168.1.4/30 is directly connected, Serial2/0

L 192.168.1.5/32 is directly connected, Serial2/0

192.168.100.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.100.0/24 is directly connected, Loopback0

L 192.168.100.1/32 is directly connected, Loopback0

R2#ping

Protocol [ip]:

Target IP address: 192.168.100.1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: 172.16.64.1

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]: record // TYPE record TO VIEW HOP BY HOP IP TRACE AND ITS RETURN PATH

Number of hops [ 9 ]:

Loose, Strict, Record, Timestamp, Verbose[RV]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

Packet sent with a source address of 172.16.64.1

Packet has IP options: Total option bytes= 39, padded length=40

Record route: <*>

(0.0.0.0)

Reply to request 0 (32 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(192.168.1.6)

(192.168.100.1)

(192.168.1.5) // R1

(172.16.64.1) <*> // BRACKET IS EXIT INTERFACE; RETURN PATH IS VIA R2 (SYMMETRIC PATH: R2 > R1 > R2)

(0.0.0.0)

End of list

Reply to request 1 (20 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.64.1) <*>

(0.0.0.0)

End of list

Reply to request 2 (16 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.64.1) <*>

(0.0.0.0)

End of list

Reply to request 3 (16 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.64.1) <*>

(0.0.0.0)

End of list

Reply to request 4 (20 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.64.1) <*>

(0.0.0.0)

End of list

Success rate is 100 percent (5/5), round-trip min/avg/max = 16/20/32 ms

R3#ping

Protocol [ip]:

Target IP address: 192.168.100.1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: 172.16.32.1

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]: record

Number of hops [ 9 ]:

Loose, Strict, Record, Timestamp, Verbose[RV]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

Packet sent with a source address of 172.16.32.1

Packet has IP options: Total option bytes= 39, padded length=40

Record route: <*>

(0.0.0.0)

Reply to request 0 (28 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.1.1) // R2

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 1 (12 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 2 (8 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 3 (28 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 4 (8 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.5)

(172.16.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/16/28 ms

R2#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#route-map PRIMARY_MED_OUT permit 10

R2(config-route-map)#set metric ?

+/-<metric> Add or subtract metric

<0-4294967295> Metric value or Bandwidth in Kbits per second

R2(config-route-map)#set metric 75 // MED IS FOR INBOUND PATH MANIPULATION; SHARED BETWEEN EBGP NEIGHBORS; LOWER IS PREFERRED

R2(config-route-map)#exit

R2(config)#router bgp 64512

R2(config-router)#neighbor 192.168.1.5 route-map PRIMARY_MED_OUT out

R2(config-router)#end

R2#

*Jul 17 13:55:02.290: %SYS-5-CONFIG_I: Configured from console by console

R2#clear ip bgp * soft

R3#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R3(config)#route-map SECONDARY_MED_OUT permit 10

R3(config-route-map)#set metric 50 // PREFER R3 FOR INBOUND ROUTES

R3(config-route-map)#exit

R3(config)#router bgp 64512

R3(config-router)#neighbor 192.168.1.1 route-map SECONDARY_MED_OUT out

R3(config-router)#end

R3#

*Jul 17 13:56:27.378: %SYS-5-CONFIG_I: Configured from console by console

R3#clear ip bgp * soft

R2#show ip bgp

BGP table version is 4, local router ID is 172.16.64.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.32.1 0 100 0 i

*> 0.0.0.0 0 32768 i

*> 192.168.100.0 192.168.1.5 0 150 0 200 i

R3#show ip bgp

BGP table version is 5, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

* i 172.16.0.0 172.16.64.1 0 100 0 i

*> 0.0.0.0 0 32768 i

* 192.168.100.0 192.168.1.1 0 125 0 200 i

*>i 172.16.64.1 0 150 0 200 i

R3#ping

Protocol [ip]:

Target IP address: 192.168.100.1

Repeat count [5]:

Datagram size [100]:

Timeout in seconds [2]:

Extended commands [n]: y

Source address or interface: 172.16.32.1

Type of service [0]:

Set DF bit in IP header? [no]:

Validate reply data? [no]:

Data pattern [0xABCD]:

Loose, Strict, Record, Timestamp, Verbose[none]: record

Number of hops [ 9 ]:

Loose, Strict, Record, Timestamp, Verbose[RV]:

Sweep range of sizes [n]:

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.100.1, timeout is 2 seconds:

Packet sent with a source address of 172.16.32.1

Packet has IP options: Total option bytes= 39, padded length=40

Record route: <*>

(0.0.0.0)

Reply to request 0 (56 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.1) // R1

(172.16.32.1) <*> // R3 > R1 > R3

(0.0.0.0)

End of list

Reply to request 1 (16 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 2 (8 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 3 (16 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Reply to request 4 (8 ms). Received packet has options

Total option bytes= 40, padded length=40

Record route:

(172.16.1.2)

(192.168.1.6)

(192.168.100.1)

(192.168.1.1)

(172.16.32.1) <*>

(0.0.0.0)

End of list

Success rate is 100 percent (5/5), round-trip min/avg/max = 8/20/56 ms

R1#show ip bgp // R1 (ISP) PREFER R3 TO REACH 172.16.0.0/16 SINCE R3 ADVERTISED A LOWER MED (50)

BGP table version is 12, local router ID is 192.168.100.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*> 172.16.0.0 192.168.1.2 50 0 64512 i // LOWER METRIC (50) PREFFERED

* 192.168.1.6 75 0 64512 i

*> 192.168.100.0 0.0.0.0 0 32768 i

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#router bgp 200

R1(config-router)#neighbor 192.168.1.6 default-originate // INJECT DEFAULT ROUTE IN BGP

R1(config-router)#neighbor 192.168.1.2 default-originate

R1(config-router)#exit

R1(config)#interface loop 10

R1(config-if)#

*Jul 17 14:11:50.942: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback10, changed state to up

R1(config-if)#ip address 10.0.0.1 255.255.255.0

R1(config-if)#end

R1#

R2#show ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is 192.168.1.5 to network 0.0.0.0

B* 0.0.0.0/0 [20/0] via 192.168.1.5, 00:00:07

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.1/32 is directly connected, Serial2/1

D 172.16.32.0/24 [90/2297856] via 172.16.1.2, 04:22:17, Serial2/1

C 172.16.64.0/24 is directly connected, Loopback0

L 172.16.64.1/32 is directly connected, Loopback0

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.4/30 is directly connected, Serial2/0

L 192.168.1.6/32 is directly connected, Serial2/0

B 192.168.100.0/24 [20/0] via 192.168.1.5, 00:42:35

R3#show ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is 172.16.64.1 to network 0.0.0.0

B* 0.0.0.0/0 [200/0] via 172.16.64.1, 00:00:31

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.2/32 is directly connected, Serial2/1

C 172.16.32.0/24 is directly connected, Loopback0

L 172.16.32.1/32 is directly connected, Loopback0

D 172.16.64.0/24 [90/2297856] via 172.16.1.1, 04:22:41, Serial2/1

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/30 is directly connected, Serial2/2

L 192.168.1.2/32 is directly connected, Serial2/2

B 192.168.100.0/24 [200/0] via 172.16.64.1, 00:42:59

R3#show ip bgp

BGP table version is 7, local router ID is 172.16.32.1

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter,

x best-external, a additional-path, c RIB-compressed,

Origin codes: i - IGP, e - EGP, ? - incomplete

RPKI validation codes: V valid, I invalid, N Not found

Network Next Hop Metric LocPrf Weight Path

*>i 0.0.0.0 172.16.64.1 0 150 0 200 i // DEFAULT ROUTE PREFER VIA R2 SINCE HIGHER LOCAL PREF

* 192.168.1.1 125 0 200 i

* i 172.16.0.0 172.16.64.1 0 100 0 i

*> 0.0.0.0 0 32768 i

* 192.168.100.0 192.168.1.1 0 125 0 200 i

*>i 172.16.64.1 0 150 0 200 i

R3#traceroute 10.0.0.1

Type escape sequence to abort.

Tracing the route to 10.0.0.1

VRF info: (vrf in name/id, vrf out name/id)

1 172.16.1.1 24 msec 16 msec 20 msec

2 192.168.1.5 [AS 200] 16 msec 32 msec 28 msec

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#interface serial 2/0

R1(config-if)#shut

R1(config-if)#

*Jul 17 14:14:55.542: %BGP-5-ADJCHANGE: neighbor 192.168.1.6 Down Interface flap

*Jul 17 14:14:55.542: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.6 IPv4 Unicast topology base removed from session Interface flap

R1(config-if)#

*Jul 17 14:14:57.514: %LINK-5-CHANGED: Interface Serial2/0, changed state to administratively down

*Jul 17 14:14:58.514: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to down

R2#

*Jul 17 14:15:25.178: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial2/0, changed state to down

*Jul 17 14:15:25.214: %BGP-5-ADJCHANGE: neighbor 192.168.1.5 Down Interface flap

*Jul 17 14:15:25.214: %BGP_SESSION-5-ADJCHANGE: neighbor 192.168.1.5 IPv4 Unicast topology base removed from session Interface flap

R2#

R2#show ip route // DEFAULT ROUTE HOPS VIA R3 DUE TO next-hop-self BETWEEN IBGP PEERS

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is 172.16.32.1 to network 0.0.0.0

B* 0.0.0.0/0 [200/0] via 172.16.32.1, 00:00:06

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.1/32 is directly connected, Serial2/1

D 172.16.32.0/24 [90/2297856] via 172.16.1.2, 04:24:59, Serial2/1

C 172.16.64.0/24 is directly connected, Loopback0

L 172.16.64.1/32 is directly connected, Loopback0

B 192.168.100.0/24 [200/0] via 172.16.32.1, 00:00:06

R3#show ip route

Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2

E1 - OSPF external type 1, E2 - OSPF external type 2

i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2

ia - IS-IS inter area, * - candidate default, U - per-user static route

o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP

+ - replicated route, % - next hop override

Gateway of last resort is 192.168.1.1 to network 0.0.0.0

B* 0.0.0.0/0 [20/0] via 192.168.1.1, 00:00:30

172.16.0.0/16 is variably subnetted, 6 subnets, 3 masks

S 172.16.0.0/16 is directly connected, Null0

C 172.16.1.0/24 is directly connected, Serial2/1

L 172.16.1.2/32 is directly connected, Serial2/1

C 172.16.32.0/24 is directly connected, Loopback0

L 172.16.32.1/32 is directly connected, Loopback0

D 172.16.64.0/24 [90/2297856] via 172.16.1.1, 04:25:23, Serial2/1

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/30 is directly connected, Serial2/2

L 192.168.1.2/32 is directly connected, Serial2/2

B 192.168.100.0/24 [20/0] via 192.168.1.1, 00:00:30

R2#traceroute 10.0.0.1 // HOP VIA R3 TO REACH 10.0.0.1

Type escape sequence to abort.

Tracing the route to 10.0.0.1

VRF info: (vrf in name/id, vrf out name/id)

1 172.16.1.2 20 msec 20 msec 20 msec

2 192.168.1.1 [AS 200] 20 msec 60 msec 24 msec

My Network Lab

Friday, April 5, 2019

Manipulating BGP Local Preference and MED

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