Hello Engineers,
Like to share one BGP neighbor example where eBGP peers are reachable but not performing neighborship.
If you already aware about this funda, then thanks for reading.
lets see the scenario.
1. Let See the BGP Config
R1#
router bgp 100
bgp router-id 1.1.1.1
bgp log-neighbor-changes
neighbor 2.2.2.2 remote-as 200
neighbor 2.2.2.2 ebgp-multihop 2
neighbor 2.2.2.2 update-source Loopback1
R2#
router bgp 200
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 22.22.22.22 mask 255.255.255.255
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 ebgp-multihop 2
neighbor 1.1.1.1 update-source Loopback1
2. Lets Check the Neighbor reachability.
R1 Routing Table:
S* 0.0.0.0/0 [1/0] via 10.10.12.2
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.10.12.0/24 is directly connected, FastEthernet0/0
L 10.10.12.1/32 is directly connected, FastEthernet0/0
11.0.0.0/32 is subnetted, 1 subnets
C 11.11.11.11 is directly connected, Loopback11
R2 Routing Table:
S* 0.0.0.0/0 [1/0] via 10.10.12.1
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.10.12.0/24 is directly connected, FastEthernet0/0
L 10.10.12.2/32 is directly connected, FastEthernet0/0
22.0.0.0/32 is subnetted, 1 subnets
C 22.22.22.22 is directly connected, Loopback22
Ping Test from R1:
R1#ping 2.2.2.2 source 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/11/12 ms
R1#
Ping Test From R2:
R2#ping 1.1.1.1 source 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, 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 = 8/14/28 ms
R2#
3. After having default route and ping connectivity, our eBGP neighbors are not coming UP.
R1#show ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 200 0 0 1 0 0 never Idle
R1#
R2#show ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1 4 100 0 0 1 0 0 never IdleR2#
4. Lets Try to Debug the BGP Messages.
R1#debug bgp all
BGP debugging is on for all address families
R1#
*Nov 5 18:30:10.919: BGP: 2.2.2.2 Active open failed - no route to peer, open active delayed 14336ms (35000ms max, 60% jitter)
R1#
5. So to make eBGP neighborship UP we need a specific route to peer even we have default route(it wont help).
R1(config)#ip route 2.2.2.2 255.255.255.255 10.10.12.2
R1#show ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 200 5 5 3 0 0 00:00:38 1
BGP Routing Table:
22.0.0.0/32 is subnetted, 1 subnets
B 22.22.22.22 [20/0] via 2.2.2.2, 00:07:16
R2#show ip bgp summary
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
1.1.1.1 4 100 5 5 3 0 0 00:00:44 1
BGP Routing Table:
11.0.0.0/32 is subnetted, 1 subnets
B 11.11.11.11 [20/0] via 1.1.1.1, 00:07:45
R1#ping 22.22.22.22 source 11.11.11.11
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 22.22.22.22, timeout is 2 seconds:
Packet sent with a source address of 11.11.11.11
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/11/12 ms
R1#
R2#ping 11.11.11.11 source 22.22.22.22
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 11.11.11.11, timeout is 2 seconds:
Packet sent with a source address of 22.22.22.22
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 4/9/12 ms
R2#
R2#
