EBGP route advertised to IBGP but unable to ping it from IBGP router

[Ashwani Pande]

Hi Experts,

need help on a lab setup. I am doing BGP between two AS and full mesh iBGP in both AS. Now after checking I am able to reach each other loopback address which I used for peering. I advertised 2 networks to far end AS and I am able to ping them from EBGP router of the other AS but as we know edge router when receives EBGP routes it advertise it one hop inside the network. I can see those routes in iBGP router but when I try to ping them from iBGP router I am unable to ping them? I have changed the next hop address as well between the router that receives that EBGP routes and iBGP router.

Topology is as below I advertised a 2 networks to R1 from R5 and both I can ping from R1 but not from R2.

One network that I advertised is loopback on R5 and other it has learned from R7 through ibgp(RIP).

[a.alekseev]

What nets did you advertise to R5?

[Ashwani Pande]

Hello,

I advertised from R5 to R1..R5-->R1. One is the loopback on R5 and other is it has learned through IGP(RIP protocol) which basically R7 advertised to R5.

[a.alekseev]

What nets did you advertise  !!!! FROM R1 TO R5?

[Ashwani Pande]

Hi From R5 towards R1.

one is 100.100.100.100/32 loopback and one is 7.7.7.7 which is the loopback of R7 as per the diagram.

R5 has learned it through IGP protocol.

[a.alekseev]

Do you understand the difference between two phrases?

"From R1 to R5" and "From R5 to R1"
Does anybody in as200 know about the route to R2?

[Ashwani Pande]

Yes R5 knows how to reach R1 and R2 as from R5 I can ping both R1 and R2.

[a.alekseev]

Oh...

pls provide the outputs:
sh ip route from R2 and R7
and
from R2
ping 7.7.7.7 source lo0

[Ashwani Pande]

output of ip route from R2

R2#sh ip route
Gateway of last resort is not set

1.0.0.0/32 is subnetted, 1 subnets
D 1.1.1.1 [90/2297856] via 192.168.1.1, 03:03:02, Serial0/0
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
100.0.0.0/32 is subnetted, 1 subnets
B 100.100.100.100 [200/0] via 1.1.1.1, 00:39:23
168.1.0.0/30 is subnetted, 1 subnets
D 168.1.1.0 [90/2681856] via 172.32.1.2, 03:03:00, Serial0/1
3.0.0.0/32 is subnetted, 1 subnets
D 3.3.3.3 [90/2297856] via 172.32.1.2, 03:03:00, Serial0/1
4.0.0.0/32 is subnetted, 1 subnets
D 4.4.4.4 [90/2809856] via 172.32.1.2, 03:03:02, Serial0/1
6.0.0.0/32 is subnetted, 1 subnets
B 6.6.6.6 [200/1] via 1.1.1.1, 00:39:27
172.32.0.0/30 is subnetted, 1 subnets
C 172.32.1.0 is directly connected, Serial0/1
7.0.0.0/32 is subnetted, 1 subnets
B 7.7.7.7 [200/2] via 1.1.1.1, 00:39:28
122.0.0.0/30 is subnetted, 1 subnets
D EX 122.1.1.0 [170/2681856] via 192.168.1.1, 02:53:17, Serial0/0
192.168.1.0/30 is subnetted, 1 subnets
C 192.168.1.0 is directly connected, Serial0/0
R2#

R2#ping 7.7.7.7 source lo0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 7.7.7.7, timeout is 2 seconds:
Packet sent with a source address of 2.2.2.2
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/20/32 ms
R2#

output from R7

2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [200/2297856] via 5.5.5.5, 00:41:29
100.0.0.0/32 is subnetted, 1 subnets
R 100.100.100.100 [120/2] via 10.1.1.2, 00:00:00, Serial0/0
20.0.0.0/30 is subnetted, 1 subnets
R 20.1.1.0 [120/1] via 10.1.1.2, 00:00:00, Serial0/0
5.0.0.0/32 is subnetted, 1 subnets
R 5.5.5.5 [120/2] via 10.1.1.2, 00:00:00, Serial0/0
6.0.0.0/32 is subnetted, 1 subnets
R 6.6.6.6 [120/1] via 10.1.1.2, 00:00:00, Serial0/0
7.0.0.0/32 is subnetted, 1 subnets
C 7.7.7.7 is directly connected, Loopback0
10.0.0.0/30 is subnetted, 1 subnets
C 10.1.1.0 is directly connected, Serial0/0
122.0.0.0/30 is subnetted, 1 subnets
R 122.1.1.0 [120/2] via 10.1.1.2, 00:00:04, Serial0/0
R7#

[a.alekseev]

>>>Topology is as below I advertised a 2 networks to R1 from R5 and both I can ping from R1 but not from R2.

What are you unable to ping?

[Ashwani Pande]

yes but I can see you have asked me to ping with source loopback of R2. earlier I was just pinging it from R2 without any source. Does it mean BGP only works if you are pinging with the router ID as a source?

Now I am able to ping R2 from R7 using source as a loopback.

can you please clear why not working in normal ping.

[a.alekseev · Accepted solution]

Look at routing table on R2
Search for the route to 7.7.7.7.
It comes from 1.1.1.1
Search for the route to 1.1.1.1
We got it via Serial0/0

What address does it have?
192.168.1.x/30
We will use this address as source address for the ping 7.7.7.7

Now, on R7, do you have the route for 192.168.1.0/30?

[anuragg]

just configure R1<>R2 IBGP neighbor with next-hop-self