[c-nsp] Sanity check OSPF/BGP

Drew Weaver drew.weaver at thenap.com
Thu Oct 8 09:00:54 EDT 2020


I have two sets of core routers due to a transition period from one set to the other.

I have noticed that when there is a connectivity disruption between the two sets of core routers and one upstream peering/edge router:

Oct  7 12:01:14 EDT: %OSPF-5-ADJCHG: Process 1, Nbr <removed> on TenGigabitEthernet2/1 from FULL to DOWN, Neighbor Down: BFD node down

<Two+ minutes of null routing traffic for no reason>

Oct  7 12:03:29 EDT: %BGP-5-ADJCHANGE: neighbor <removed> Down BGP Notification sent

What I expect to happen is:

              The route to the peering edge router's loopback interface is withdrawn when OSPF/OSPFv3 closes.
              The core router will close the BGP session when the route to the dead peering edge router is withdrawn and will begin using one of the 5 other copies of the same route that it has.

Things I have implemented to avoid this:

              The peering edge router and the core routers peer with IP addresses that are only learnable via OSPF and aren't available in any other protocol. [It's not part of our IP space]

I guess I just need a sanity check regarding whether my assumption that it shouldn't be null routing traffic for 2+ minutes if one of our peering edge routers gets hit by a meteor is correct since we have 5 peering edge routers.

Thanks in advance friends,

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