[189542] in North American Network Operators' Group
Re: rfc 1812 third party address on traceroute
daemon@ATHENA.MIT.EDU (William Herrin)
Wed Jun 1 17:46:10 2016
X-Original-To: nanog@nanog.org
X-Really-To: <nanog@nanog.org>
In-Reply-To: <046D8339-24D3-4A8C-BE4A-4D1A1097916A@voipgate.com>
From: William Herrin <bill@herrin.us>
Date: Wed, 1 Jun 2016 17:45:41 -0400
To: Marc Storck <mstorck@voipgate.com>
Cc: North American Network Operators' Group <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
On Wed, Jun 1, 2016 at 3:16 PM, Marc Storck <mstorck@voipgate.com> wrote:
>> .-----------------.
>> | |
>> | B |--------- D
>> S ---------| A R |
>> | C |--------- (toward S)
>> | |
>> `-----------------'
>>
> With BCP38 in mind, could there be situations
> where Router R is not allowed to source packets
> with address A out of interface C?
Hi Marc,
I think you're right. Address A in a /30 from ISP A. ISP C accepts
source addresses from your /24 but not the A /30. So if the router
does not follow the RFC (sends an ICMP packet out C with a source
address from A), typical asynchronous routing can result in
black-holding the ICMP error message.
You've hit on a good reason to follow the RFC by default instead of
doing what Randy wants. ;)
-Bill
--
William Herrin ................ herrin@dirtside.com bill@herrin.us
Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>
