nanog mailing list archives
Re: private ip addresses from ISP
From: Daniel Senie <dts () senie com>
Date: Tue, 23 May 2006 09:36:30 -0400
At 09:22 AM 5/23/2006, Robert Bonomi wrote:
> Date: Tue, 23 May 2006 03:33:34 -0400 > From: Richard A Steenbergen <ras () e-gerbil net> > To: nanog () nanog org > Subject: Re: private ip addresses from ISP > > > 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? > ... > > Sorry to dig this up from last week but I have to strongly disagree with > > point #3. > > >From RFC 1918 > > Because private addresses have no global meaning, routing information > > about private networks shall not be propagated on inter-enterprise > > 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. I quote, from the material cited above: " ..., and packets with private source or destination addresses should not be forwarded across such links. ... " There are some types of packets that can legitimately have RFC1918 source addresses -- 'TTL exceeded' for example -- that one should legitimately allow across network boundaries.
Really? You really want TTL-E messages with RFC1918 source addr? Even if they're used as part of a denial of service attack? Even though you can't tell where they actually came from?
> 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. *I* care. When those packets contain 'malicious' content, for example. When the provider =cannot= tell me which of _their_own_customers_ originated that attack, for example. (This provider has inbound source-filtering ontheir Internet 'gateway' routers, but *not* on their customer-facing equipment(either inbound or outbound.)
So you really don't want ANY packets with RFC 1918 source addresses then, not even ICMP TTL-E messages, since they could be used in a malicious fashion, and you would not be able to determine the true origin.
It's even more comical when the NSP uses RFC1918 space internally, and does *not* filter those source addresses from their customers.
You mean like Comcast using Cisco routers in their head-ends and having the 10/8 address show up in traceroutes and so forth? Not sure to what degree it's the NSP's fault vs. the router vendors', but yes.
> There are semi-legitimate reasons for > packets with those sources addresses to float around the Internet, and > they don't hurt anything. I guess you don't mind paying for transit of packets that _cannot_possibly_ have any legitimate purpose on your network.
Along with this goes the usual flamewar over RFC 2827, ingress filtering (of which URPF is a subset implementation).
Some of us, on the other hand, _do_ object.
And some of us pay for bandwidth, care about getting congestion problems from useless traffic, etc. Perhaps it makes the case a lot clearer for selling "better than equal" service to the highest bidder if your network is overrun with undesired traffic.
Current thread:
- RE: private ip addresses from ISP, (continued)
- RE: private ip addresses from ISP David Schwartz (May 17)
- RE: private ip addresses from ISP Andrew Kirch (May 22)
- Re: private ip addresses from ISP Hyunseog Ryu (May 22)
- Re: private ip addresses from ISP Richard A Steenbergen (May 23)
- Re: private ip addresses from ISP Edward B. DREGER (May 23)
- Re: private ip addresses from ISP Patrick W. Gilmore (May 23)
- Re: private ip addresses from ISP Richard A Steenbergen (May 23)
- Re: private ip addresses from ISP sthaug (May 23)
- Re: private ip addresses from ISP Patrick W. Gilmore (May 23)
- Re: private ip addresses from ISP Daniel Senie (May 23)
- RE: private ip addresses from ISP Frank Bulk (May 23)
- Re: private ip addresses from ISP Joe Maimon (May 23)
- RE: private ip addresses from ISP Brian Johnson (May 23)
- Re: private ip addresses from ISP Joe Maimon (May 23)
- Re: private ip addresses from ISP Joseph S D Yao (May 23)
- Re: private ip addresses from ISP Joe Maimon (May 23)
- Re: private ip addresses from ISP Joseph S D Yao (May 23)