BGP not sending hellos

[grapevine]

I am trying to form an EBGP adjaceny and they are not peering R6 and R8. Please advise

They are directly connected

Configuration below:

R6#sh run | s bgp
router bgp 3
no synchronization
bgp log-neighbor-changes
neighbor 9.9.9.9 remote-as 89
neighbor 9.9.9.9 update-source Loopback1
neighbor 9.9.9.9 soft-reconfiguration inbound
no auto-summary

R6#sh ip bgp summ
BGP router identifier 6.6.6.6, local AS number 3
BGP table version is 2, main routing table version 2
1 network entries using 132 bytes of memory
1 path entries using 52 bytes of memory
2/1 BGP path/bestpath attribute entries using 336 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
Bitfield cache entries: current 1 (at peak 1) using 32 bytes of memory
BGP using 552 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
9.9.9.9 4 89 0 0 0 0 0 never Idle

R6#ping 9.9.9.9

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 9.9.9.9, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/28/32 ms

R8#sh run | s bgp
router bgp 89
no synchronization
bgp log-neighbor-changes
neighbor 6.6.6.6 remote-as 3
neighbor 6.6.6.6 update-source Loopback1
neighbor 6.6.6.6 soft-reconfiguration inbound
no auto-summary

R8#sh ip bgp summ
BGP router identifier 9.9.9.9, local AS number 89
BGP table version is 3, main routing table version 3
2 network entries using 264 bytes of memory
2 path entries using 104 bytes of memory
2/1 BGP path/bestpath attribute entries using 336 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 704 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
6.6.6.6 4 3 0 0 0 0 0 never Idle

R8#ping 6.6.6.6

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 6.6.6.6, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/27/32 ms

[MHM Cisco World · Accepted solution]

Only you need this 

Neighbor x.x.x.x ebgp multihop 

You use LO not direct connect IP so ebgp is far than one ttl that why ebgp failed 

MHM

[grapevine]

Thanks for the quick response! That worked I was breaking my head for more than two hours.

[paul driver]

Hello @grapevine 

FYI -
IBGP peering has a default TTL value of 255
EBGP peering has a default TTL value of 1

So when you try ebgp peering via loopback interfaces, those interfaces are not directly connected as such the TTL would become 2 the EBGP peering will not establish

Appending the multihop by itself , the ttl value will increase by default to 255 which is not really necessary, so you could just specify the multihop with a value, which means the ebgp peering can be up that hop value away

example
neighbour x.x.x. multihop 2

Additionally there is also BGP TTL neighbour security this is a bgp security feature that also states a TTL value but this value is absolute meaning the bgp peering have to be match otherwise the peering will not establish.

Note: TTL neighbour security/ Multihop are mutually exclusive to each other , so not to used at the same time