rfc 1812 third party address on traceroute

Marc Storck mstorck at voipgate.com
Wed Jun 1 21:50:28 UTC 2016


I'm not saying anyone is wrong here. I merely want to point out eventual incompatabilities.

So please don't get me wrong.

Regards,

Marc

> On 1 juin 2016, at 23:46, William Herrin <bill at herrin.us> wrote:
> 
> On Wed, Jun 1, 2016 at 3:16 PM, Marc Storck <mstorck at 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 at dirtside.com  bill at herrin.us
> Owner, Dirtside Systems ......... Web: <http://www.dirtside.com/>



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