On Mon, May 22, 2006 at 04:30:37PM -0400, Andrew Kirch wrote:
3) You are seeing packets with source IPs inside private space arriving at your interface from your ISP?
...
From RFC 1918 Because private addresses have no global meaning, routing information about private networks shall not be propagated on inter-enterprise
Sorry to dig this up from last week but I have to strongly disagree with point #3. links, and packets with private source or destination addresses should not be forwarded across such links. Routers in networks not using private address space, especially those of Internet service providers, are expected to be configured to reject (filter out) routing information about private networks.
The ISP shouldn't be "leaving" anything to the end-user, these packets should be dropped as a matter of course, along with any routing advertisements for RFC 1918 space(From #1). ISP's who leak 1918 space into my network piss me off, and get irate phone calls for their trouble.
The section you quoted from RFC1918 specifically addresses routes, not packets. If you're receiving RFC1918 *routes* from anyone, you need to thwack them over the head with a cluebat a couple of times until the cluey filling oozes out. If you're receiving RFC1918 sourced packets, for the most part you really shouldn't care. There are semi-legitimate reasons for packets with those sources addresses to float around the Internet, and they don't hurt anything. If you really can't stand seeing an RFC1918 sourced packet over the Internet it is more of a personality problem than a networking problem, so a good shrink is probably going to be more useful than a good firewall. -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)