New router feature - icmp error source-interface

Chris,

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

 http://m
omo.lcs.mit.edu/traceroute/index.php

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

- ferg



-- "Chris L. Morrow" <christopher.morrowverizonbusiness.com> wrote:

[snip]

What's interesting is that today, in many networks, the
usefulness of
traceeroute has bee degraded by other non-ip issues
(<cough>mpls</cough>)
not in ALL cases, but certainly in many you are not seeing
quite what
you'd expect from the traceroute :(



--
"Fergie", a.k.a. Paul Ferguson
 Engineering Architecture for the Internet
 fergdawg(at)netzero.net
 ferg's tech blog: http://fergdawg.blogspo
t.com/

On Tue, 26 Sep 2006, Fergie wrote:

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


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
though...

On Tue, Sep 26, 2006 at 02:51:21AM +0000, Fergie wrote:
> 
> So, I'm wondering: What happens when you have a
traceroute tool
> that shows you MPLS-lableled hops, too? 
> 
>  http://m
omo.lcs.mit.edu/traceroute/index.php
> 
> The best (?) of both worls, but I digress...

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.

-- 
Richard A Steenbergen <rase-gerbil.net>       http://www.e-gerbil.net/r
as
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41
5ECA F8B1 2CBC)