In this chapter we are going to see IBGP Neighborship between non-connected routers i.e. using Loopback interfaces.
Here R1 , R2 , R3 and R4 belongs to AS 100 i.e same AS .
We need to configure BGP on R1 & R4 which are non-connected routers.
This will be IBGP since R1 & R4 both belongs to same AS .
We will be using loopback interfaces IP address as BGP peer IP address.
We would need an IGP to provide connectivity between loopback interfaces of R1 and R4.
ie. we should able to ping R4's loopback 4.4.4.4 from R1 keeping source R1's loopback 1.1.1.1 & vice versa.
So lets configure EIGRP on all routers i.e R1 , R2 , R3 & R4.
Note :- We are not using physical interfaces IP address because if the link goes down the bgp peering will go although it have alternate path . Loopback interfaces are logical interfaces and they never go down even if the physical interfaces goes since they would have reachability from the alternate link.
LETS CHECK THE IP ADDRESSES AND STATUS FOR THE INTERFACES ON ALL ROUTERS
R1#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R2
Se1 up up TO R3
Se2 admin down down
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 13.1.1.1 YES manual up up
Serial2 unassigned YES unset administratively down down
R2#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R1
Se1 up up TO R4
Se2 admin down down
R2#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 12.1.1.2 YES manual up up
Serial1 24.1.1.2 YES manual up up
Serial2 unassigned YES unset administratively down down
R3#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R4
Se1 up up TO R1
Se2 admin down down
R3#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 34.1.1.3 YES manual up up
Serial1 13.1.1.3 YES manual up up
Serial2 unassigned YES unset administratively down down
R4#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R3
Se1 up up to R2
Se2 admin down down
R4#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 34.1.1.4 YES manual up up
Serial1 24.1.1.4 YES manual up up
Serial2 unassigned YES unset administratively down down
CONFIGURATION OF EIGRP ALL THE ROUTERS
R1(config)#router eigrp 10
R1(config-router)#network 12.1.1.0 255.255.255.0
R1(config-router)#network 13.1.1.0 255.255.255.0
R1(config-router)#network 1.1.1.1 255.255.255.255
R1(config-router)#^Z
R2(config)#router eigrp 10
R2(config-router)#network 12.1.1.0 255.255.255.0
R2(config-router)#network 24.1.1.0 255.255.255.0
R2(config-router)#network 2.2.2.2 255.255.255.255
R2(config-router)#^Z
R3(config)#router eigrp 10
R3(config-router)#network 13.1.1.0 255.255.255.0
R3(config-router)#network 34.1.1.0 255.255.255.0
R3(config-router)#network 3.3.3.3 255.255.255.255
R3(config-router)#^Z
R4(config)#router eigrp 10
R4(config-router)#network 24.1.1.0 255.255.255.0
R4(config-router)#network 34.1.1.0 255.255.255.0
R4(config-router)#network 4.4.4.4 255.255.255.255
R4(config-router)#^Z
!! Testing Loopback to Loopback Reachability for R1 & R4
R1#ping 4.4.4.4 source loopback 0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/52/64 ms
R4#ping 1.1.1.1 source loopback 0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 4.4.4.4
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/41/56 ms
Lets Configure IBGP between R1 and R4 using loopback interfaces.
R1(config)#router bgp 100
R1(config-router)#neighbor 4.4.4.4 remote-as 100
R1(config-router)#neighbor 4.4.4.4 update-source loopback 0
R1(config-router)#^Z
!
R4(config)#router bgp 100
R4(config-router)#neighbor 1.1.1.1 remote-as 100
R4(config-router)#neighbor 1.1.1.1 update-source loopback 0
R4(config-router)#^Z
Log on R1
Dec 20 01:19:13.015: %BGP-5-ADJCHANGE: neighbor 4.4.4.4 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
4.4.4.4 4 100 5 5 1 0 0 00:01:24 0
R4#sh ip bgp summary
BGP router identifier 4.4.4.4, 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
1.1.1.1 4 100 5 5 1 0 0 00:01:45 0
Points to Remember
•We can configure iBGP Neighborship between Non-connected routers.
•The Peer IP’s should have reachability between each others.
The Loopback interfaces are more preferred since they don’t go down even if an link goes down .The reachability between loopback interfaces can be achieved via alternate path
Here R1 , R2 , R3 and R4 belongs to AS 100 i.e same AS .
 |
| IBGP |
We need to configure BGP on R1 & R4 which are non-connected routers.
This will be IBGP since R1 & R4 both belongs to same AS .
We will be using loopback interfaces IP address as BGP peer IP address.
We would need an IGP to provide connectivity between loopback interfaces of R1 and R4.
ie. we should able to ping R4's loopback 4.4.4.4 from R1 keeping source R1's loopback 1.1.1.1 & vice versa.
So lets configure EIGRP on all routers i.e R1 , R2 , R3 & R4.
Note :- We are not using physical interfaces IP address because if the link goes down the bgp peering will go although it have alternate path . Loopback interfaces are logical interfaces and they never go down even if the physical interfaces goes since they would have reachability from the alternate link.
LETS CHECK THE IP ADDRESSES AND STATUS FOR THE INTERFACES ON ALL ROUTERS
R1#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R2
Se1 up up TO R3
Se2 admin down down
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 13.1.1.1 YES manual up up
Serial2 unassigned YES unset administratively down down
R2#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R1
Se1 up up TO R4
Se2 admin down down
R2#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 12.1.1.2 YES manual up up
Serial1 24.1.1.2 YES manual up up
Serial2 unassigned YES unset administratively down down
R3#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R4
Se1 up up TO R1
Se2 admin down down
R3#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 34.1.1.3 YES manual up up
Serial1 13.1.1.3 YES manual up up
Serial2 unassigned YES unset administratively down down
R4#sh int des
Interface Status Protocol Description
Fa0 admin down down
Se0 up up TO R3
Se1 up up to R2
Se2 admin down down
R4#sh ip int brief
Interface IP-Address OK? Method Status Protocol
FastEthernet0 unassigned YES unset administratively down down
Serial0 34.1.1.4 YES manual up up
Serial1 24.1.1.4 YES manual up up
Serial2 unassigned YES unset administratively down down
CONFIGURATION OF EIGRP ALL THE ROUTERS
R1(config)#router eigrp 10
R1(config-router)#network 12.1.1.0 255.255.255.0
R1(config-router)#network 13.1.1.0 255.255.255.0
R1(config-router)#network 1.1.1.1 255.255.255.255
R1(config-router)#^Z
R2(config)#router eigrp 10
R2(config-router)#network 12.1.1.0 255.255.255.0
R2(config-router)#network 24.1.1.0 255.255.255.0
R2(config-router)#network 2.2.2.2 255.255.255.255
R2(config-router)#^Z
R3(config)#router eigrp 10
R3(config-router)#network 13.1.1.0 255.255.255.0
R3(config-router)#network 34.1.1.0 255.255.255.0
R3(config-router)#network 3.3.3.3 255.255.255.255
R3(config-router)#^Z
R4(config)#router eigrp 10
R4(config-router)#network 24.1.1.0 255.255.255.0
R4(config-router)#network 34.1.1.0 255.255.255.0
R4(config-router)#network 4.4.4.4 255.255.255.255
R4(config-router)#^Z
!! Testing Loopback to Loopback Reachability for R1 & R4
R1#ping 4.4.4.4 source loopback 0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/52/64 ms
R4#ping 1.1.1.1 source loopback 0
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 4.4.4.4
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/41/56 ms
Lets Configure IBGP between R1 and R4 using loopback interfaces.
R1(config)#router bgp 100
R1(config-router)#neighbor 4.4.4.4 remote-as 100
R1(config-router)#neighbor 4.4.4.4 update-source loopback 0
R1(config-router)#^Z
!
R4(config)#router bgp 100
R4(config-router)#neighbor 1.1.1.1 remote-as 100
R4(config-router)#neighbor 1.1.1.1 update-source loopback 0
R4(config-router)#^Z
Log on R1
Dec 20 01:19:13.015: %BGP-5-ADJCHANGE: neighbor 4.4.4.4 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
4.4.4.4 4 100 5 5 1 0 0 00:01:24 0
R4#sh ip bgp summary
BGP router identifier 4.4.4.4, 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
1.1.1.1 4 100 5 5 1 0 0 00:01:45 0
Points to Remember
•We can configure iBGP Neighborship between Non-connected routers.
•The Peer IP’s should have reachability between each others.
The Loopback interfaces are more preferred since they don’t go down even if an link goes down .The reachability between loopback interfaces can be achieved via alternate path
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