mpls, vpnv4 and /32 addresses
Hi, I'm trying to understand the reason why you should use /32 addresses when peering mp-bgp peers for vpnp4 address exchange.
I've seen that the whole reason of this requirement is that you're supposed to use multihop bgp with ospf as the igp, thus leading to the ospf issue of advertising a loopback in /32 regardless of the actual subnet mask used.
Therefore I've made a test and the solution is either using a native /32 in the loopback or changing ospf network type of loopback to point-to-point, which makes everything match.
However I still not understand what exactly goes wrong when you don't use one of the fixes above, I think that the problem lies between the last "p" router and the "pe" because the "pe" has an e.g. /24 loopback while the "p" is fooled by ospf into thinking that it's a /32.
The questions is: and so? even if there's a mismatch the last "p" router is supposed to strip off the top label, so the packet arrives to the "pe" only with the inner label, for which he has a proper lib, fib, lfib etc.
Sorry for the long question, and explanation is deeply appreciated.