BGP Peers not establishing three way handshake!!!

[Kasiraman S]

All,

I have below topology and I do not know why the RTR R5 and R6 and not initiating eBGP neighbor relationship. I have removed the config and readded, I reloaded the rtr but did not help. I have bidirectional connectivity between the Routers but not initiating three way handshake. Please advise.

R1---eBGP--R3-------R6---eBGP---R8

                    \        /

                     \     /

                      R5

                     /    \

                   /        \

                R4         R7

R5#show run | sec router bgp
router bgp 345
no synchronization
bgp log-neighbor-changes
bgp confederation peers 67
neighbor 3.3.3.3 remote-as 345
neighbor 3.3.3.3 update-source Loopback0
neighbor 4.4.4.4 remote-as 345
neighbor 4.4.4.4 update-source Loopback0
neighbor 6.6.6.6 remote-as 67
neighbor 6.6.6.6 update-source Loopback0
no auto-summary

R5#show ip b s
BGP router identifier 5.5.5.5, local AS number 345
BGP table version is 4, main routing table version 4
2 network entries using 234 bytes of memory
3 path entries using 156 bytes of memory
3/1 BGP path/bestpath attribute entries using 372 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
BGP using 762 total bytes of memory
BGP activity 2/0 prefixes, 3/0 paths, scan interval 60 secs

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
3.3.3.3         4   345      26      25        4    0    0 00:21:29        2
4.4.4.4         4   345      26      25        4    0    0 00:21:26        1
6.6.6.6         4    67       0       0        0    0    0 never   Idle

R5#ping 6.6.6.6 so loop0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
Packet sent with a source address of 5.5.5.5
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/16/44 ms
----------------------------------------------------------------------------------

R6#show run | sec router bgp
router bgp 67
no synchronization
bgp log-neighbor-changes
bgp confederation peers 345
neighbor 5.5.5.5 remote-as 345
neighbor 5.5.5.5 update-source Loopback0
neighbor 7.7.7.7 remote-as 67
neighbor 7.7.7.7 update-source Loopback0
no auto-summary

R6#show ip b s
BGP router identifier 6.6.6.6, local AS number 67
BGP table version is 1, main routing table version 1

Neighbor        V    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  State/PfxRcd
5.5.5.5         4   345       0       0        0    0    0 never    Idle
7.7.7.7         4    67      23      22        1    0    0 00:19:40        0

R6#ping 5.5.5.5 so loop 0

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 6.6.6.6
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/21/40 ms

Thanks,

Kasi

[Reza Sharifi · Accepted solution]

Hi Kasi,

add this command to each router

neighbor 6.6.6.6 ebgp-multihop 1 

neighbor 5.5.5.5 ebgp-multihop 1 

Since this is EBGP and you are sourcing it from a looopback address and not physical you need EBGP multihop 
command

HTH
Reza

[Kasiraman S]

Hi Reza,

Yes you are correct. Thanks a lot. I did not realise this simple point.

Thanks,kasi

[Reza Sharifi]

No worries, it happens to all of us!!!

Glad to help

Reza