Is that a dark fiber P2P or a an ISP provided "L2 over L3 P2P"? If it's the latter like an eLine link - could they be re-routing traffic on their underlay where the mtu changes maybe?
-----Original Message----- From: cisco-nsp <[email protected]> On Behalf Of Richard Mikisa Sent: Tuesday, July 9, 2019 11:58 AM To: [email protected] Subject: [c-nsp] OSPF flapping between Nexus 7000 and ASR 1001x This message originates from outside of your organisation. Hi All, I am running OSPF across a point to point link between a Nexus 7000 and an ASR1000x. The OSPF works fine but every couple of hours, it breaks and neighbor state goes into EXCHANGE and remains there for another 40 minutes or so. It then goes into full, OSPF comes up and all is well for another couple of hours or so and then the cycle starts again. All the time, IP connectivity between the two point to point IPs is up. Configuration as below.. ASR1001x#sh run int g0/0/1 interface GigabitEthernet0/0/1 description ** MPLS London - SO031732 ** mtu 9216 ip address 10.32.250.17 255.255.255.252 ip ospf network point-to-point ip ospf mtu-ignore negotiation auto cdp enable end ASR1000x#sh ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 40.1.1.1 0 EXCHANGE/ - 00:00:33 10.32.250.18 GigabitEtherne t0/0/1 10.32.8.253 1 FULL/DR 00:00:32 10.32.250.1 GigabitEtherne t0/0/0 On the Nexus N7K1-LON-AGG# sh run int vlan 3960 interface Vlan3960 no shutdown mtu 9216 ip address 10.32.250.18/30 ip ospf cost 1 ip ospf network point-to-point no ip ospf passive-interface ip ospf mtu-ignore ip router ospf 100 area 0.0.0.32 N7K1-LON-AGG# sh ip ospf neighbors 10.32.250.2 OSPF Process ID 100 VRF default Total number of neighbors: 15 Neighbor ID Pri State Up Time Address Interface 10.32.250.2 1 EXCHANGE/ - 00:05:06 10.32.250.17 Vlan3960 N7K1-LON-AGG# And the logs on the ASR Jul 9 14:33:00.682: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from FULL to DOWN, Neighbor Down: Too many retransmissions Jul 9 14:34:00.683: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from DOWN to DOWN, Neighbor Down: Ignore timer expired Jul 9 14:34:46.962: %CLNS-5-ADJCHANGE: ISIS (Overlay1): Adjacency to N7K1-LON-OTV (Overlay1) Down, hold time expired Jul 9 14:39:56.543: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from EXCHANGE to DOWN, Neighbor Down: Interface down or detached Jul 9 14:55:20.865: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from EXCHANGE to DOWN, Neighbor Down: Interface down or detached .Jul 9 15:06:25.955: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from EXCHANGE to DOWN, Neighbor Down: Too many retransmissions .Jul 9 15:07:25.955: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from DOWN to DOWN, Neighbor Down: Ignore timer expired .Jul 9 15:37:57.514: %OSPF-5-ADJCHG: Process 100, Nbr 40.1.1.1 on GigabitEthernet0/0/1 from LOADING to FULL, Loading Done .Jul 9 15:38:03.296: %CLNS-5-ADJCHANGE: ISIS (Overlay1): Adjacency to 8478.AC22.FEC3 (Overlay1) Up, new adjacency .Jul 9 15:42:25.399: %SEC_LOGIN-5-LOGIN_SUCCESS: Login Success [user: richard.mikisa] [Source: 10.0.1.2] [localport: 22] at 15:42:25 UTC Tue Jul 9 2019 Can someone advise on where to look? -- cheers Richard _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/ _______________________________________________ cisco-nsp mailing list [email protected] https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
