IBGP not getting EBGP routes (nevermind)

bermovick

Whew. These BGP labs are rough; but that's how we learn.

I think I'm starting to get the hang of the basics; my current lab is redistributing nicely and EBGP is working well across a frame-relay (admittedly the easiest type), but for some reason my IBGP isn't working and I can't seem to figure out why. I'm going to flip back through and see what I'm missing but putting this out here too for others to look at in case I have a blind spot as we sometimes do.

I have a screenshot and the information that I think is important; if anything else is needed ask and I'll provide.

Routers 1, 2, and 3 are getting everything (including R's 4-7), but R's 4-7 are only getting the other internal BGP route (6 is getting 7's and 7 is getting 6's, for example). Synchronization is off (default).




[EDIT] Figured it out. I didn't think R2 & R3 would need to ALSO advertise the 10.0.0.0/24 network (the frame-relay net) since R1 was, but they do; and it (mostly) makes sense. I'll need to ponder it a bit more and see where my logic was off.

bermovick

I think I figured it out, once I had a chance to sleep on it. Once you remember that (I?)BGP won't add a route unless it's reachable, it's easy to see that the 31000 and 32000 AS's wouldn't add any routes for the other AS's unless they knew how to reach them (have the route to the 10.0.0.0/24 network). Once they know that, the rest of the dominoes fall like a house of cards. Checkmate.

Does that sound correct, or am I off still?

networker050184

Next hop reachability. When the routes aren't working take a look at the next hop and see if you have a route to it.

Most people will manually set the next hop on the edge to prevent this type of thing.

bermovick

Yeah; I think what I was thinking was that R1 would tell R2 and R3 about their common 10.0.0.0 network, so R2/R3 would have it from that; and then pass it on to the R4-R7 devices. I guess it makes more sense that since its directly connected, R2/3 would be "whatever dude" when R1 tries to tells them about it, but then be unable to tell R4-R7 about it since I hadn't told 2 & 3 they could.