Hi Reza,
Thanks for the reply. Yes, I've used the show ip eigrp topology command many times in troubleshooting this, and the prefix just doesn't appear at all from the distribution.
This is a layer 3 routed design (no VLANs spanned from the distribution). There are other 6500s and 3750s connected to the distribution, but they are getting the T2 prefixes as they should.
* T2, which is originating the prefix, has routed gig uplinks to D1 and D2.
* D1 and D2 have an interregion routed gig link.
* F1 and F2 have dual routed gig uplinks to D1 and D2.
* N1 and N2 are Nexus 5548s that were just installed that have routed 10 gig uplinks to F1 and F2. They also have an interregion between themselves.
T2 is advertising the prefixes to D1 and D2. D1 and D2 are advertising the prefixes between each other and to F2. F2 is advertising the prefixes to N1 and N2. N1 and N2 are advertising the prefixes to F1.
Looking at the metrics, D1 and D2 should be advertising the routes to F1. They are advertising other prefixes to F1. T2's prefixes are the only prefixes that F1 is getting through N1 and N2. If I turn off the links between F1 and N1/N2, F1 doesn't have the prefixes at all. By sheer coincidence, the traffic ends up taking the correct links to D1 and D2 because of the default route.
Neighbor relationships are in place and functional, as evidenced by the fact that F1 is getting other prefixes from D1 and D2. Again, there are no distribute lists, route maps, passive interfaces, redistribution, no variance commands, neither F1 nor F2 is stubbed, N1 and N2 have delays on their 10 gig links to make those routes less palatable. The routes that F1 is using are very much not preferred; the FD F1 is using is 8448, whereas if D1 and D2 were advertising to F1 they would have an AD of 3072, which would make F1's FD about 3328 (educated guess based on what's happening on other links). And this is ONLY happening with T2's prefixes. Using some careful output filtering, it was quickly apparent that this was going on with three prefixes and they all originate from T2. But other access switches are getting the prefixes just fine.
It just flat out looks like EIGRP is deciding not to advertise the prefixes to F1 for reasons completely unknown to me.
I'm sure there's a debug command I could use, but this is our data center distribution, and I tend toward being very protective of my distribution switches when it comes to debug commands. So that's why I was hoping there was a command that I was missing that would just tell me what it was advertising to a specific neighbor.
Thank you for taking the time to reply!
