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BGP Flapping

We have p2p link between SanDeago and Mexico, configured with BGP.

 

in recent times the link is plapping continuously, plz check below bgp config on both routers.

 

NatPen_MX_3825#sh run | be bgp
router bgp 65001
 no synchronization
 bgp log-neighbor-changes
 network 10.60.0.0 mask 255.255.0.0
 redistribute static metric 20 route-map MXCAMMAP
 neighbor 10.63.0.1 remote-as 1
 neighbor 10.63.0.1 fall-over
 no auto-summary
!


NatPen_MX_3825#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 10.63.0.1 to network 0.0.0.0

     199.220.41.0/30 is subnetted, 1 subnets
B       199.220.41.176 [20/0] via 10.63.0.1, 00:00:13
     1.0.0.0/24 is subnetted, 1 subnets
B       1.4.204.0 [20/0] via 10.63.0.1, 00:00:13
     152.177.0.0/30 is subnetted, 1 subnets
B       152.177.74.24 [20/0] via 10.63.0.1, 00:00:13
     152.181.0.0/30 is subnetted, 1 subnets
B       152.181.185.68 [20/0] via 10.63.0.1, 00:00:13
     206.113.119.0/26 is subnetted, 2 subnets
B       206.113.119.128 [20/0] via 10.63.0.1, 00:00:13
B       206.113.119.0 [20/0] via 10.63.0.1, 00:00:13
     199.220.194.0/30 is subnetted, 1 subnets
B       199.220.194.232 [20/0] via 10.63.0.1, 00:00:13
     172.17.0.0/30 is subnetted, 1 subnets
B       172.17.29.0 [20/0] via 10.63.0.1, 00:00:13
     172.16.0.0/24 is subnetted, 1 subnets
B       172.16.1.0 [20/0] via 10.63.0.1, 00:00:13
     172.18.0.0/30 is subnetted, 2 subnets
B       172.18.30.0 [20/0] via 10.63.0.1, 00:00:13
B       172.18.29.0 [20/0] via 10.63.0.1, 00:00:13
     172.21.0.0/30 is subnetted, 1 subnets
D       172.21.106.120 [220/63232] via 172.20.107.229, 5d03h, Serial2/0
     172.20.0.0/30 is subnetted, 1 subnets
C       172.20.107.228 is directly connected, Serial2/0
     172.23.0.0/30 is subnetted, 1 subnets
B       172.23.9.0 [20/0] via 10.63.0.1, 00:00:13
     172.22.0.0/30 is subnetted, 2 subnets
B       172.22.0.144 [20/0] via 10.63.0.1, 00:00:13
D       172.22.157.84 [220/63232] via 172.20.107.229, 5d03h, Serial2/0
     172.32.0.0/24 is subnetted, 1 subnets
B       172.32.7.0 [20/0] via 10.63.0.1, 00:00:13
     10.0.0.0/8 is variably subnetted, 21 subnets, 5 masks
B       10.30.0.0/21 [20/0] via 10.63.0.1, 00:00:13
B       10.31.0.0/16 [20/0] via 10.63.0.1, 00:00:13
B       10.30.13.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.20.0.0/16 [20/0] via 10.63.0.1, 00:00:14
B       10.21.0.0/16 [20/0] via 10.63.0.1, 00:00:14
B       10.40.0.0/16 [20/0] via 10.63.0.1, 00:00:14
B       10.41.0.0/16 [20/0] via 10.63.0.1, 00:00:14
C       10.63.0.0/16 is directly connected, GigabitEthernet0/1
S       10.61.1.0/24 [1/0] via 10.60.0.2
C       10.60.0.0/16 is directly connected, GigabitEthernet0/0
B       10.100.0.44/30 [20/0] via 10.63.0.1, 00:00:14
B       10.133.201.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.100.0.32/30 [20/0] via 10.63.0.1, 00:00:14
B       10.90.0.0/16 [20/0] via 10.63.0.1, 00:00:14
B       10.172.16.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.4.204.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.4.205.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.3.202.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.4.202.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.4.201.0/24 [20/0] via 10.63.0.1, 00:00:14
B       10.254.254.240/32 [20/0] via 10.63.0.1, 00:00:14
     147.225.0.0/30 is subnetted, 1 subnets
B       147.225.40.160 [20/0] via 10.63.0.1, 00:00:14
B    206.169.74.0/24 [20/0] via 10.63.0.1, 00:00:14
B    192.168.100.0/24 [20/0] via 10.63.0.1, 00:00:14
B*   0.0.0.0/0 [20/0] via 10.63.0.1, 00:00:14
NatPen_MX_3825#sh ip bg
NatPen_MX_3825#sh ip bgp
BGP table version is 32518, local router ID is 172.20.107.230
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 0.0.0.0          10.63.0.1                              0 1 65000 65000 i
*> 1.4.204.0/24     10.63.0.1                              0 1 ?
*> 10.3.202.0/24    10.63.0.1                              0 1 ?
*> 10.4.201.0/24    10.63.0.1                              0 1 ?
*> 10.4.202.0/24    10.63.0.1                              0 1 ?
*> 10.4.204.0/24    10.63.0.1                              0 1 ?
*> 10.4.205.0/24    10.63.0.1                              0 1 ?
*> 10.20.0.0/16     10.63.0.1                              0 1 65000 65000 ?
*> 10.21.0.0/16     10.63.0.1                              0 1 65000 65000 i
*> 10.30.0.0/21     10.63.0.1                0             0 1 i
*> 10.30.13.0/24    10.63.0.1                0             0 1 i
*> 10.31.0.0/16     10.63.0.1                0             0 1 ?
*> 10.40.0.0/16     10.63.0.1                              0 1 65000 65000 i
*> 10.41.0.0/16     10.63.0.1                              0 1 65000 65000 ?
*> 10.60.0.0/16     0.0.0.0                  0         32768 i
*> 10.61.1.0/24     10.60.0.2               20         32768 ?
r> 10.63.0.0/16     10.63.0.1                0             0 1 ?
*> 10.90.0.0/16     10.63.0.1                              0 1 65000 10 i
*> 10.100.0.32/30   10.63.0.1                              0 1 ?
*> 10.100.0.44/30   10.63.0.1                              0 1 65000 65000 ?
*> 10.133.201.0/24  10.63.0.1                              0 1 ?
*> 10.172.16.0/24   10.63.0.1                              0 1 ?
*> 10.254.254.240/32
                    10.63.0.1                              0 1 ?
*> 147.225.40.160/30
                    10.63.0.1                0             0 1 ?
*> 152.177.74.24/30 10.63.0.1                              0 1 65000 ?
*> 152.181.185.68/30
                    10.63.0.1                              0 1 65000 ?
*> 172.16.1.0/24    10.63.0.1                              0 1 ?
*> 172.17.29.0/30   10.63.0.1                              0 1 65000 65000 ?
*> 172.18.29.0/30   10.63.0.1                0             0 1 ?
*> 172.18.30.0/30   10.63.0.1                              0 1 ?
*> 172.22.0.144/30  10.63.0.1                              0 1 ?
*> 172.23.9.0/30    10.63.0.1                              0 1 65000 65000 ?
*> 172.32.7.0/24    10.63.0.1                              0 1 ?
*> 192.168.100.0    10.63.0.1                              0 1 ?
*> 199.220.41.176/30
   Network          Next Hop            Metric LocPrf Weight Path
                    10.63.0.1                              0 1 ?
*> 199.220.194.232/30
                    10.63.0.1                              0 1 65000 ?
*> 206.113.119.0/26 10.63.0.1                              0 1 65000 65004 ?
*> 206.113.119.128/26
                    10.63.0.1                              0 1 65000 65004 ?
*> 206.169.74.0     10.63.0.1                              0 1 65000 65000 ?
NatPen_MX_3825#

NatPen_MX_3825#sh run | in ip rou
ip route 10.61.1.0 255.255.255.0 10.60.0.2
NatPen_MX_3825#

===============================================================================================================

 

router bgp 1
 no synchronization
 bgp log-neighbor-changes
 network 10.30.0.0 mask 255.255.248.0
 network 10.30.13.0 mask 255.255.255.0
 redistribute connected
 neighbor 10.63.0.2 remote-as 65001
 neighbor 10.63.0.2 fall-over
 neighbor 147.225.40.161 remote-as 65000
 neighbor 147.225.40.161 distribute-list no-redist-CV-Routes out
 neighbor 172.18.29.2 remote-as 1
 no auto-summary


NatPen_SD2#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route

Gateway of last resort is 147.225.40.161 to network 0.0.0.0

     199.220.41.0/30 is subnetted, 1 subnets
B       199.220.41.176 [200/0] via 10.100.0.34, 3w1d
     1.0.0.0/24 is subnetted, 1 subnets
B       1.4.204.0 [200/0] via 10.133.201.254, 3w1d
     152.177.0.0/30 is subnetted, 1 subnets
B       152.177.74.24 [20/0] via 147.225.40.161, 4w3d
     152.181.0.0/30 is subnetted, 1 subnets
B       152.181.185.68 [20/0] via 147.225.40.161, 4w3d
     206.113.119.0/26 is subnetted, 2 subnets
B       206.113.119.128 [20/0] via 147.225.40.161, 4w3d
B       206.113.119.0 [20/0] via 147.225.40.161, 4w3d
     199.220.194.0/30 is subnetted, 1 subnets
B       199.220.194.232 [20/0] via 147.225.40.161, 4w0d
     172.17.0.0/30 is subnetted, 1 subnets
B       172.17.29.0 [20/0] via 147.225.40.161, 3w0d
     172.16.0.0/24 is subnetted, 1 subnets
B       172.16.1.0 [200/0] via 10.133.201.254, 3w1d
     172.18.0.0/30 is subnetted, 2 subnets
B       172.18.30.0 [200/0] via 172.18.29.2, 3w1d
C       172.18.29.0 is directly connected, FastEthernet1/1
     172.23.0.0/30 is subnetted, 1 subnets
B       172.23.9.0 [20/0] via 147.225.40.161, 1w2d
     172.22.0.0/30 is subnetted, 1 subnets
B       172.22.0.144 [200/0] via 172.18.29.2, 3w1d
     172.32.0.0/24 is subnetted, 1 subnets
B       172.32.7.0 [200/0] via 10.133.201.254, 3w1d
     10.0.0.0/8 is variably subnetted, 21 subnets, 5 masks
C       10.30.0.0/21 is directly connected, GigabitEthernet0/0.1
C       10.31.0.0/16 is directly connected, GigabitEthernet0/0.2
C       10.30.13.0/24 is directly connected, GigabitEthernet0/0.2
B       10.20.0.0/16 [20/0] via 147.225.40.161, 4w0d
B       10.21.0.0/16 [20/0] via 147.225.40.161, 4w3d
B       10.40.0.0/16 [20/0] via 147.225.40.161, 1w2d
B       10.41.0.0/16 [20/0] via 147.225.40.161, 1w2d
C       10.63.0.0/16 is directly connected, GigabitEthernet0/1
B       10.61.1.0/24 [20/20] via 10.63.0.2, 00:01:44
B       10.60.0.0/16 [20/0] via 10.63.0.2, 00:01:44
B       10.100.0.44/30 [20/0] via 147.225.40.161, 4w3d
B       10.133.201.0/24 [200/0] via 172.18.29.2, 3w1d
B       10.100.0.32/30 [200/0] via 172.18.29.2, 3w1d
B       10.90.0.0/16 [20/0] via 147.225.40.161, 4w3d
B       10.172.16.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.4.204.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.4.205.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.3.202.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.4.202.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.4.201.0/24 [200/0] via 10.133.201.254, 3w1d
B       10.254.254.240/32 [200/0] via 10.133.201.254, 3w1d
     147.225.0.0/30 is subnetted, 1 subnets
C       147.225.40.160 is directly connected, Serial3/0
B    206.169.74.0/24 [20/0] via 147.225.40.161, 2w1d
B    192.168.100.0/24 [200/0] via 10.133.201.254, 3w1d
B*   0.0.0.0/0 [20/0] via 147.225.40.161, 3w5d
NatPen_SD2#


NatPen_SD2#sh run | in ip route
ip route 0.0.0.0 0.0.0.0 10.133.201.254 210
ip route 1.4.205.147 255.255.255.255 10.100.0.29
ip route 170.146.36.16 255.255.255.255 10.100.0.29
ip route 170.146.234.48 255.255.255.255 10.100.0.29
NatPen_SD2#

 

 

 

1 REPLY

Hello.I would check logs for

Hello.

I would check logs for events, happened at the same moment as route flap. Also I would check 'sh ip bgp summ" to see how long current BGP session us up.

I think BGP session was reestablished, that caused route flap - on ND2 router 10.60.0.0/16 is only 1 minute old.

The flap might be caused by inteface (G0/1) status or, maybe, 10.63.0.2 (.1) was learnt with longer-match via another interface/routing protocol.

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