[48588] in North American Network Operators' Group
Re: Bogon list
daemon@ATHENA.MIT.EDU (Stephen J. Wilcox)
Sat Jun 8 16:56:24 2002
Date: Sat, 8 Jun 2002 21:55:49 +0100 (BST)
From: "Stephen J. Wilcox" <steve@opaltelecom.co.uk>
To: North America Network Operators Group Mailing List <nanog@merit.edu>
Cc: Stephen Griffin <stephen.griffin@rcn.com>,
"Sean M. Doran" <smd@clock.org>
In-Reply-To: <20020607165508.0AC3CAC@proven.weird.com>
Errors-To: owner-nanog-outgoing@merit.edu
Indeed, you should filter ingress packets with your own addresses for
security and as you say using non globally unique addresses will therefore
cause it to break pMTU.
I concede!!
Steve
On Fri, 7 Jun 2002, Greg A. Woods wrote:
>
> [ On Friday, June 7, 2002 at 10:26:53 (+0100), Stephen J. Wilcox wrote: ]
> > Subject: Re: Bogon list
> >
> > RFC1918 does not break path-mtu, filtering it does tho..
>
> So, in other words inappropriate use of RFC 1918 does not break Path MTU
> Discovery! You can't still have your cake and have eaten it too. One
> way or another RFC 1918 addresses must not be let past the enterprise
> boundaries. Lazy and/or ignorant people don't always meet all the
> requirements of RFC 1918, but it's only their lack of compliance that
> _may_ allow Path-MTU-discovery to continue working for their networks
> for _some_ people _some_ of the time.
>
> However any enterprise also using RFC 1918, but using it correctly (or
> customers of such an enterprise), and thus who are also carefully
> protecting their use from interference by outside parties, will be
> filtering inbound packets with source addresses in the RFC 1918 assigned
> networks, and so as a result they _will_ experience Path-MTU-discovery
> failure (i.e. at any time it's necessary it literally cannot work) when
> attempting to contact (and sometimes be contacted by, depending on the
> application protocol in use) any host on or behind the lazy and/or
> ignorant operator's network(s).
>
> (and no, I'm not sorry if I've yet again offended anyone who might be
> mis-using RFC 1918 addresses for public nodes -- you should all know
> better by now! How many _years_ has it been?)
>
> > > 2) Not believe in filtering RFC1918 sourced traffic at enterprise boundaries
> > > (of which an exchange would be a boundary)
> >
> > What for? You'll find many more much more mailicious packets coming from
> > legit routable address space.
>
> If you have any IP address level trust relationsips on your internal
> LANs then you _MUST_ (if you want those trust relationships to be valid)
> filter all foreign packets with source addresses appearing to be part of
> your internal LANs.
>
> > For p2p you can use unnumbered.. it wont work on exchanges but i agree
> > they shouldnt be rfc1918.
>
> On this we can agree! :-)
>
>
