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Usage of BGP Next-Hop_self

on the topology above I have R1 and R2 on AS12 and R3 on AS3

I am using Next-Hop-Self on R2 to tell R1 "in order to reach R3 come to me", but does not seem to work.

Here is the configuration of BGP on each router.

R1#sh run | beg router bgp
router bgp 12
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 192.168.12.2 remote-as 12

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R2#sh run | beg router bgp
router bgp 12
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.168.12.1 remote-as 12
 neighbor 192.168.12.1 next-hop-self
 neighbor 192.168.23.3 remote-as 3
 neighbor 192.168.23.3 next-hop-self

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R3#sh run | beg router bgp
router bgp 3
 no synchronization
 bgp log-neighbor-changes
 network 3.3.3.0 mask 255.255.255.0
 neighbor 192.168.23.2 remote-as 12

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I cannot ping from R1 to R3 and vice-versa

If I advertize networks 192.168.12.0 and 192.168.23.0 From R2 then I will be able to ping from R1 to R3 and back

Any idea ?

Thanks

Predrag Jovic

You don't need to advertise transit networks. But, if you are not advertising transit networks you need to ping with address from "known IP address" (IP address that is currently placed in routing table. I guess you are pinging from/to address that is not currently in routing table of one or more devices.
Ping from R1 to R3
ping 3.3.3.1
If source address is not specified ping is using as source interface that is closest to destination (interfaces with IP addresses 192.168.12.1) and if you did not advertised transit routes destination for ICMP echo will be unknown.
So
ping 3.3.3.1 source 1.1.1.1
should solve pinging problem (of course if network for addresses 1.1.1.1 and 3.3.3.3 are advertised in the networks).

jskfan

ASKER

I advertized just 192.168.12.0 From R2
and now I can ping from R1 to R3 , but still cannot ping from R3 to R1

jskfan

ASKER

Probably that's how it supposed to be in real word, you do not advertise transit networks. in this scenario I am not supposed to advertize 192.168.23.0/24 network from R2..
as such, if pinging from R3 to R1 does not reply..it is normal...

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Predrag Jovic

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jskfan

ASKER

Thank you

Predrag Jovic

You're welcome.