[189495] in North American Network Operators' Group
Re: rfc 1812 third party address on traceroute
daemon@ATHENA.MIT.EDU (Octavio Alvarez)
Tue May 31 12:08:48 2016
X-Original-To: nanog@nanog.org
To: Randy Bush <randy@psg.com>,
North American Network Operators' Group <nanog@nanog.org>
From: Octavio Alvarez <octalnanog@alvarezp.org>
Date: Tue, 31 May 2016 09:08:42 -0700
In-Reply-To: <m2r3cihl96.wl%randy@psg.com>
Errors-To: nanog-bounces@nanog.org
On 05/30/2016 10:03 PM, Randy Bush wrote:
> rfc1812 says
>
> 4.3.2.4 ICMP Message Source Address
>
> Except where this document specifies otherwise, the IP source address
> in an ICMP message originated by the router MUST be one of the IP
> addresses associated with the physical interface over which the ICMP
> message is transmitted. If the interface has no IP addresses
> associated with it, the router's router-id (see Section [5.2.5]) is
> used instead.
>
> some folk have interpreted this to mean that, if a router R has three
> interfaces
>
> .-----------------.
> | |
> | B |--------- D
> S ---------| A R |
> | C |--------- (toward S)
> | |
> `-----------------'
>
> of course, simpletons such as i would desire the source of the time
> exceeded message to be A. after all, this is the interface to which i
> sent the icmp with the TTL to expire.
Do you mean the source address or the source interface?
I'm not sure if you mean that, if sent through C it should have the
source addres of A, or that it should actually be sent through A
regardless of the routing table (which sounds better to me).
Octavio.
