General question on rfc1918

Joe Abley jabley at
Tue Nov 13 15:39:47 UTC 2007

On 13-Nov-2007, at 10:35, Robert Bonomi wrote:

>> On 13-Nov-2007, at 10:08, Drew Weaver wrote:
>>>       Hi there, I just had a real quick question. I hope this is
>>> found to be on topic.
>>> Is it to be expected to see rfc1918 src'd packets coming from
>>> transit carriers?
>> You should not send packets with RFC1918 source or destination
>> addresses to the Internet. Everybody should follow this advice. If
>> everybody did follow that advice, you wouldn't see the packets you  
>> are
>> seeing.
> Really?  What do you do if a 'network internal' device -- a legitimate
> use of RFC1918 addresses -- discovers 'host/network unreachable' for  
> an
> external-origin packet transitinng that device?   <evil grin>

You drop the packet at your border before it is sent out to the  

This is why numbering interfaces in the data path of non-internal  
traffic is a bad idea.

> Packets which are strictly error/status reporting -- e.g. IMP  
> 'unreachable',
> 'ttl exceeded', 'redirect', etc. -- should *NOT* be filtered at  
> network
> boundaries  _solely_ because of an RFC1918 source address.

I respectfully disagree.


More information about the NANOG mailing list