GRE packets

Thu Jun 18 02:20:48 UTC 1998

In message <199806171954.PAA14489 at all-purpose-gunk.near.net>, John Hawkinson writes:
> > Anyone have a definitive list or info on network operators who definately
> > allow or definately disallow GRE packets across their networks.
> > 
> > Sorry for the semi-operational content :)
> 
> It's hard to imagine any serious network providers who would
> block arbitrary kinds of traffic.

Several others have posted replies on this topic, but they've missed the most
common situation. I've seen (major) network providers with the following
access rules in their routers:

	allow tcp
	allow udp
	allow icmp
	deny *

While not explicitly blocking GRE, they're implicitly dropping everything
(including IPsec traffic, which is how I found this; my corporate VPNs weren't
working :-).

Of course, trying to get this resolved took *weeks*, because I couldn't talk
to anybody who understood that there were protocols besides the ones listed
above... *sigh.

-- 
Harald Koch <chk at utcc.utoronto.ca>