[189539] in North American Network Operators' Group
Re: rfc 1812 third party address on traceroute
daemon@ATHENA.MIT.EDU (Hugo Slabbert)
Wed Jun 1 17:08:41 2016
X-Original-To: nanog@nanog.org
Date: Wed, 1 Jun 2016 14:08:37 -0700
From: Hugo Slabbert <hugo@slabnet.com>
To: Octavio Alvarez <octalnanog@alvarezp.org>
In-Reply-To: <574F4DAD.9040103@alvarezp.org>
Cc: North American Network Operators' Group <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
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On Wed 2016-Jun-01 14:03:41 -0700, Octavio Alvarez <octalnanog@alvarezp.org=
> wrote:
>On 05/31/2016 11:22 AM, William Herrin wrote:
>>> 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).
>>
>> That doesn't make sense. There may be multiple next hops out A. If the
>> next hop in the FIB is out C, how would the router pick the next hop
>> to send to out A?
>
>Back to the physical address that sent the TTL-offending packet.
Which comes back to my question:
What guarantees do you have that the device at that physical address (so,=
=20
adjacent off of R's interface A) has a valid route for S, and that the=20
route does not simply point back to R?
>> Anyway, Randy's comment was about source address selection, not
>> routing. With the packet coming from S into interface A, he'd prefer
>> that the ICMP error message be sourced from the IP address assigned to
>> A, not the IP address assigned to C or R.
>
>Thanks.
--=20
Hugo Slabbert | email, xmpp/jabber: hugo@slabnet.com
pgp key: B178313E | also on Signal
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