rfc 1812 third party address on traceroute

[octalnanog at alvarezp.org (Octavio Alvarez)]

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.

> 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.