Advertising iBGP route to eBGP

Hi all,

Obviously I’m missing something here. I created this lab in GNS3 using 3725’s. I want to advertise the 11.1.1.1/24 router from ibgp R1 to ebgp R3. I added route reflector command on R2 to reflect R1’s route to R3 since I’m not using a static route. Below is my configuration:

image

===================================================================

R1//////////////////////////////////////////////////////////
interface Loopback1
ip address 11.1.1.1 255.255.255.0
!
router bgp 1
no synchronization
bgp log-neighbor-changes
network 11.1.1.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 1
neighbor 2.2.2.2 update-source Loopback0
no auto-summary
!
ip forward-protocol nd
ip route 2.2.2.2 255.255.255.255 172.16.10.2
!
R2////////////////////////////////////////////////////////
router bgp 1
no synchronization
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 1
neighbor 1.1.1.1 update-source Loopback0
neighbor 1.1.1.1 route-reflector-client
neighbor 3.3.3.3 remote-as 2
neighbor 3.3.3.3 ebgp-multihop 2
neighbor 3.3.3.3 update-source Loopback0
no auto-summary
!
ip forward-protocol nd
ip route 1.1.1.1 255.255.255.255 172.16.10.1
ip route 3.3.3.3 255.255.255.255 172.16.20.3
!

R3/////////////////////////////////////////////////////

router bgp 2
no synchronization
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 1
neighbor 2.2.2.2 ebgp-multihop 2
neighbor 2.2.2.2 update-source Loopback0
no auto-summary
!
ip forward-protocol nd
ip route 2.2.2.2 255.255.255.255 172.16.20.2

=========================================================================================
So if I do a “show ip bgp” I see this:

R3#sh ip bgp
BGP table version is 4, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path
*> 11.1.1.0/24 2.2.2.2 0 1 i
Also additional commands:

R3#sh ip bgp 11.1.1.0
BGP routing table entry for 11.1.1.0/24, version 4
Paths: (1 available, best #1, table Default-IP-Routing-Table)
Not advertised to any peer
1
2.2.2.2 from 2.2.2.2 (2.2.2.2)
Origin IGP, localpref 100, valid, external, best

R3#sh ip route bgp
11.0.0.0/24 is subnetted, 1 subnets
B 11.1.1.0 [20/0] via 2.2.2.2, 00:36:23

However if I try to ping it won’t complete.

R3#ping 11.1.1.1 source 172.16.20.3

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 172.16.20.3

Can anyone help please?

Thanks!!!

Mike

Hi Mike,
R3 is receiving the route 11.1.1.0/24, there is no problem. But the problem is that, R1 is not aware of the prefix 172.16.20.0/29. So when you are trying to ping the traffic is reaching R1 but reply traffic is not coming. If you check the routing table of R1 then you will have no roure for 172.16.20.0/29 there. Please fix this issue. To solve it there are multiple possible way.
BR
Naser