RE: private ip addresses from ISP
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Robert Bonomi Sent: Tuesday, May 23, 2006 9:22 AM To: nanog@nanog.org Cc: davids@webmaster.com Subject: Re: private ip addresses from ISP
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
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
addresses -- 'TTL exceeded' for example -- that one should legitimately allow across network boundaries.
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
packets source 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 on their Internet 'gateway' routers, but *not* on their customer-facing equipment (either inbound or outbound.)
It's even more comical when the NSP uses RFC1918 space internally, and does *not* filter those source addresses from their customers.
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.
Some of us, on the other hand, _do_ object.
YMMV
Well said, I think that Robert has done a phenomenal job of summing up my point. I don't want this trash on my network. The pertinent RFC says it shouldn't be entering my network from *your* network (for varying values of your). I don't buy the argue that the end user should decide what traffic they do and don't want when the RFC states unequivocally that the traffic shouldn't be there. Even reasonably large networks are often run by people with no appreciable networking experience, MCSE, MCP MCP+I etc. This is a simple fact of life. Andrew
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Andrew Kirch