This is a *single area* ospf environment, that has been stable for years. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network
I have seen this in the lab before, was related to the size of the LSA.
Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ?
You can check this with a ping of your mtu size set with the df bit set
.and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing
If you have a large amount of routers in your area the LSA size will grow, we saw a problem in testing when we injected 2000 prefixes into the area and the OSPF neighbour would not come up. On a cisco router you can set 'buffers huge' as a work around. Richard