From owner-nanog@merit.edu Tue Nov 13 09:12:04 2007 Cc: "nanog@merit.edu" <nanog@merit.edu> From: Joe Abley <jabley@ca.afilias.info> To: Drew Weaver <drew.weaver@thenap.com> Subject: Re: General question on rfc1918 Date: Tue, 13 Nov 2007 10:10:26 -0500
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> Your comment _is_ "generally correct", but there are some significant 'corner cases' that do complicate life. Packets that could conceivably generate a reply/response and have an RFC 1918 address (source -or- dest) should be ingress *and* egress filtered -- unless there is specific agreement with the adjacent network with regard to coordinated use of specific portions of that space. 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.