BGP - loopback addresses und ip address not reachable after next hop

[beta_admin66]

Hi,

I built a small lab with 5 routers. On some routers I have distributed the loopback addresses on the network.

R1:

router bgp 100
bgp log-neighbor-changes
neighbor 10.1.1.2 remote-as 200
neighbor 10.1.2.2 remote-as 300

R1#show ip route

B 4.4.4.4 [20/0] via 10.1.1.2, 00:01:24
6.0.0.0/32 is subnetted, 1 subnets
B 6.6.6.6 [20/0] via 10.1.2.2, 00:01:24

R2:

router bgp 200
bgp router-id 2.2.2.2
bgp log-neighbor-changes
neighbor 10.1.1.1 remote-as 100
neighbor 10.24.1.2 remote-as 400

R3:

router bgp 300
bgp log-neighbor-changes
neighbor 10.1.2.1 remote-as 100
neighbor 10.36.1.2 remote-as 400

R4:

router bgp 400
bgp router-id 4.4.4.4
bgp log-neighbor-changes
network 4.4.4.4 mask 255.255.255.255
neighbor 10.24.1.1 remote-as 200

R6:

router bgp 400
bgp log-neighbor-changes
network 6.6.6.6 mask 255.255.255.255
neighbor 10.25.1.1 remote-as 400
neighbor 10.36.1.1 remote-as 300

But I can not ping the loopback adresses. 

Can you help me?

Thanks.

[MHM Cisco World]

This not work' R1 know LO of R4/R6

But are R4/R6 dont know any IP from R1 ?

So the R1 use ip unknown from R4/R6 and hence the ping drop

Simple solution is redistrubte connect in all router. 

MHM

[David Ruess]

Hello,

While R1 has the route to the 6.6.6.6 address the R6 router doesn't have any way to get back to R1. You need to advertise a network from R1 into the BGP domain to get propagated to R6. Then when you issue a ping make sure you ping with a source address of the loopback as that's all that's reachable to the BGP peers.

-David

[paul driver]

Hello
Assumption is your bgp peering is via directly attached interfaces?
Aslo it looks like you have incomplete ibgp peering in AS400, R4-R6 requires ibgp peering between each other so the bgp reachability information pertaining to a next hop is updated so each AS400 ebep/ibgp rtr will advetise itself as a nexthop for bgp preifxes external to AS400

R4
neigbour <r6> next-hop-self

R6
neigbour <r4> next-hop-self