ā10-08-2015 03:46 PM - edited ā03-08-2019 02:07 AM
We have 3 separate 3850 connected to 6807 with fiber
and timers on interfaces are
ip ospf dead-interval 3
ip ospf hello-interval 1
3850-1 have couple times per day
Port-channel1 from FULL to DOWN, Neighbor Down: Dead timer expired Port-channel1 from LOADING to FULL, Loading Done
3850-2 have couple times per week
Port-channel1 from FULL to DOWN, Neighbor Down: Dead timer expired Port-channel1 from LOADING to FULL, Loading Done
3850-3 no logs OSPF is stable
no errors on all switche interfaces
fiber were cleaned
3850-1 switch was replaced, but still have issue.
Cisco support recommend use default timers to resolve issue. Any idea? Is it timer issue? Any way running OSPF?
Thank you.
ā10-08-2015 06:20 PM
If it's not causing any issues, you probably don't need to worry. The purpose of dead timers is to consider the link no longer valid after the timer has expired, due to a lack of OSPF hellos.
If you want, you can increase your dead timer a little bit, to 5 seconds, and the link flapping or going down for 3 seconds won't give you the error, but that won't fix your link flapping. Be aware that dead timers must to match between OSPF neighbors or the neighborship breaks, so if you change on one, change it on the rest.
Your issue isn't with OSPF itself, it's caused by those links dropping for more than 3 seconds at any given time. You can try swapping to different fibers to see if it resolves the issue.
ā10-09-2015 08:58 AM
I cleaned fiber, replace SFP's on both ends. No errors on interfaces. CPU 5-10% .
ā10-09-2015 03:18 AM
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If the links aren't actually dropping, you may just be losing the hello packets within a burst of other traffic. Do the ports indicate any drops?
What kind of link is this? I assume Ethernet, as you mention using 3850s, but will the link indicate a link down to both sides? If it does, default times should be fine. Only if the link doesn't indicate link down to both sides do you need to depend on the routing protocol's loss of neighbor timers.
If that's what's happening, you either need to increase the overall dead time interval (this to try to get some hellos outside a burst event), or you need to increase the number of hello packets within the same time interval (this to try to have some hello get through by having more [in your case fast hellos, or, if supported on the 3850, BPD]), or you use QoS to insure hello packets are protected against other traffic during burst events.
ā10-09-2015 08:54 AM
no errors on interfaces
no traffic on switches, just connected to Core.
fiber is multy mode and single mode (short distance just other building)
Core switches CPU ~20%
3850 does not support BFD
ā10-09-2015 05:22 AM
Hello
on the spoke ospf peers
enable debug
Debutg ip ospf hello
debug ip ospf adj
and post the output
Res
Paul
ā10-09-2015 08:45 AM
3850-1#
000222: Oct 7 20:44:53.933 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from FULL to DOWN, Neighbor Down: Dead timer expired
000223: Oct 7 20:44:53.936 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from DOWN to INIT, Received Hello
000224: Oct 7 20:44:53.936 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from INIT to 2WAY, 2-Way Received
000225: Oct 7 20:44:53.936 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from 2WAY to EXSTART, AdjOK?
000226: Oct 7 20:44:53.945 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from EXSTART to EXCHANGE, Negotiation Done
000227: Oct 7 20:44:53.962 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from EXCHANGE to LOADING, Exchange Done
000228: Oct 7 20:44:53.962 PDT: %OSPF-5-ADJCHG: Process 20, Nbr 10.1.1.254 on Port-channel2 from LOADING to FULL, Loading Done
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