New router feature - icmp error source-interface [was: icmp rpf]


So, I'm wondering: What happens when you have a traceroute tool
that shows you MPLS-lableled hops, too? :slight_smile:

The best (?) of both worls, but I digress...

- ferg

:slight_smile: depends on the network I guess... I'm not sure it's going to tell you
anything about hops hidden by mpls lsp's that don't decrement ttl

That doesn't show any more or less data about the path, just some extra
info about the label that is effectively useless to end users. If TTL
decrement is not enabled, all of the IP hops are hidden by the tunnel,
which is the point Chris was making.

But that said, I personally think Cisco MPLS with TTL decrement enabled
but returning the the same rtt as the penultimate hop for every IP hop
inside the LSP has caused far more harm to every NOC ticket queue on the
planet than just hiding the damn things. While we're asking for silly
features, I can name a LOT of people who would pay good money for a
dedicated ICMP generating processor on Cisco that doesn't spike every time
BGP scanner runs. Silencing end users who have figured out how to work
traceroute (or worse MTR) is worth its weight in gold.