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In message <199806171954.PAA14489@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@utcc.utoronto.ca>