Friday, 24 April 2020

BGP CHAPTER 3 - ROUTER ID

BGP Router Identifier (BGP RID)-


It is the highest loopback IP address and in absence of loopback interface/s it will be the highest IP address of an active physical interface.

BGP Router must have BGP RID to establish BGP Peer session.

BGP router id can be also manually configured using bgp router-id command .

But once it is configured the bgp session will be reset.



R1#sh ip int brief

Interface                  IP-Address      OK? Method Status                Protocol

FastEthernet0              unassigned      YES unset  administratively down down

Serial0                    12.1.1.1        YES manual up                    up

Serial1                    unassigned      YES unset  administratively down down

Serial2                    unassigned      YES unset  administratively down down


!! Currently BGP Router ID is 12.1.1.1


R1#sh ip bgp summary | i BGP router


BGP router identifier 12.1.1.1, local AS number 100


!! Configuration of loopback 0


R1(config)#int loopback 0

R1(config-if)#ip address 1.1.1.1 255.255.255.255

R1(config-if)#^Z


!! Change in BGP RID would need to reset the BGP sessions.HARD RESET IS REQUIRED .

Soft reset wont change the BGP RID .


R1#clear ip bgp *

R1#clear ip bgp all peer-group

Dec 11 11:11:39.911: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Down User reset

Dec 11 11:11:40.867: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Up

R1#sh ip bgp summary

BGP router identifier 1.1.1.1, local AS number 100

BGP table version is 1, main routing table version 1


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

12.1.1.2        4   200      17      17        1    0    0 00:00:04        0



!! Configuration of loopback 1



R1(config)#int loopback 1

R1(config-if)#ip

Dec 11 11:17:25.827: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1, changed state to up

R1(config-if)#ip add

R1(config-if)#ip address  11.11.11.11 255.255.255.255

R1(config-if)#^Z



R1#clear ip bgp *

Dec 11 11:17:50.691: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Down User reset

Dec 11 11:17:51.323: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Up

R1#sh ip bgp summary

BGP router identifier 11.11.11.11, local AS number 100

BGP table version is 1, main routing table version 1



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

12.1.1.2        4   200      27      27        1    0    0 00:00:02        0



R1(config)#no interface loopback 0

R1(config)#no interface loopback 1

R1(config)#int

Dec 11 11:19:42.095: %LINK-5-CHANGED: Interface Loopback0, changed state to administratively down

Dec 11 11:19:43.095: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to down

R1(config)#int

Dec 11 11:19:43.623: %LINK-5-CHANGED: Interface Loopback1, changed state to administratively down

Dec 11 11:19:44.623: %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback1, changed state to down

R1(config)#^Z

R1#

Dec 11 11:19:47.491: %SYS-5-CONFIG_I: Configured from console by console

R1#clear ip bgp *

R1#config

Dec 11 11:19:52.691: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Down User reset

R1#sh ip bgp summary

Dec 11 11:19:53.771: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Up

R1#sh ip bgp summary

BGP router identifier 12.1.1.1, local AS number 100

BGP table version is 1, main routing table version 1



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

12.1.1.2        4   200      33      33        1    0    0 00:00:01        0

R1#



!! Setting BGP RID Manually




R1(config)#

R1(config)#router bgp 100

R1(config-router)#bgp router-id 100.1.1.1

R1(config-router)#^Z

R1#

Dec 11 11:21:49.995: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Down Router ID changed

R1#

Dec 11 11:21:51.003: %SYS-5-CONFIG_I: Configured from console by console

Dec 11 11:21:51.267: %BGP-5-ADJCHANGE: neighbor 12.1.1.2 Up

R1#sh ip bgp sum

BGP router identifier 100.1.1.1, local AS number 100

BGP table version is 1, main routing table version 1



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

12.1.1.2        4   200      38      38        1    0    0 00:00:12        0



Guys !!!! Please do remember once BGP RID is hard-cored the bgp session will be reset .

This may impact the production . So please be careful .



R2#sh ip bgp neighbors 12.1.1.1

BGP neighbor is 12.1.1.1,  remote AS 100, external link

  BGP version 4, remote router ID 100.1.1.1

  BGP state = Established, up for 00:00:44

  Last read 00:00:44, last write 00:00:44, hold time is 180, keepalive interval is 60 seconds

  Neighbor capabilities:

    Route refresh: advertised and received(old & new)

    Address family IPv4 Unicast: advertised and received

  Message statistics:

    InQ depth is 0

    OutQ depth is 0

                         Sent       Rcvd

    Opens:                  6          6

    Notifications:          0          0

    Updates:                0          0

    Keepalives:            41         41


Thanks for Reading !!!!!

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