OSPF ADJ FLAPPING

[Nirmalbang]

Hi All,

I am facing a strange issues forming adjacency between Cisco 3850 and a fortigate. There are two redundant p2p link. On one link every thing is working fine but one a second link the adjacency is flapping.I am posting here a log which continuously i am getting on 3850. If any one here can suggest what further can i check to resolve this adjacency problem.

Oct 24 16:11:18.965: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from FULL to INIT, 1-Way
Oct 24 16:11:18.973: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from INIT to 2WAY, 2-Way Received
Oct 24 16:11:18.974: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from 2WAY to EXSTART, AdjOK?
Oct 24 16:11:18.993: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXSTART to EXCHANGE, Negotiation Done
Oct 24 16:11:19.020: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXCHANGE to LOADING, Exchange Done
Oct 24 16:11:19.020: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from LOADING to FULL, Loading Done
Oct 24 16:34:16.084: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from FULL to INIT, 1-Way
Oct 24 16:34:16.093: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from INIT to 2WAY, 2-Way Received
Oct 24 16:34:16.093: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from 2WAY to EXSTART, AdjOK?
Oct 24 16:34:16.139: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXSTART to EXCHANGE, Negotiation Done
Oct 24 16:34:16.170: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXCHANGE to LOADING, Exchange Done
Oct 24 16:34:16.170: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from LOADING to FULL, Loading Done
Oct 24 16:34:26.214: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from FULL to INIT, 1-Way
Oct 24 16:34:26.223: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from INIT to 2WAY, 2-Way Received
Oct 24 16:34:26.223: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from 2WAY to EXSTART, AdjOK?
Oct 24 16:34:26.242: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXSTART to EXCHANGE, Negotiation Done
Oct 24 16:34:26.270: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXCHANGE to LOADING, Exchange Done
Oct 24 16:34:26.270: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from LOADING to FULL, Loading Done
Oct 24 16:34:40.795: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from FULL to INIT, 1-Way
Oct 24 16:34:40.803: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from INIT to 2WAY, 2-Way Received
Oct 24 16:34:40.803: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from 2WAY to EXSTART, AdjOK?
Oct 24 16:34:40.822: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXSTART to EXCHANGE, Negotiation Done
Oct 24 16:34:40.849: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from EXCHANGE to LOADING, Exchange
Oct 24 16:34:40.849: %OSPF-5-ADJCHG: Process 1, Nbr 1.0.0.1 on GigabitEthernet2/0/11 from LOADING to FULL, Loading Done
Nbang_GPX_L3#terminal no mo
Nbang_GPX_L3#terminal no monitor
Nbang_GPX_L3#unde
Nbang_GPX_L3#undebug al
Nbang_GPX_L3#undebug all
All possible debugging has been turned off
Nbang_GPX_L3#
 

[Georg Pauwen]

Hello,

redundant meaning one is active and the other not ? Make sure hello and dead timers are exchanged (both Cisco and Fortigate default to 10 and 40 seconds respectively).

[Nirmalbang]

No both the links are active active and i had tried setting up the hello and dead interval at both end still the flapping is happening

[Georg Pauwen]

Hello,

is the interface where the flapping occurs configured as OSPF network type point to point ? Can you post the output of 'show ip ospf interface ?

[Nirmalbang]

Hi, This is really strange but i changed the interface ip of both cisco and fortigate and reconfigured ospf and now things are working fine, really a strange behavior. Thanks for your help