Re: IPIP Tunnelling.

David Woodhouse (D.W.Woodhouse@nortel.co.uk)
Thu, 14 Aug 1997 15:21:13 +0100

kuznet@ms2.inr.ac.ru said:
> I'd not believe rfc2003 very much. Seems, this document is pretty
> raw. F.e. ttl handling proposed there contradicts to robusteness
> principle: it proposes to allow to set it to preconfigured value.
> Well, I did it... It was the only case in my practice when I managed
> to kill Cisco :-). When tunnels loop it look like Big Bang.

Hmmm. Setting the ttl to the same as in the encapsulated packet kills
traceroute a bit. Why can't we just refuse to IP-encapsulate any packets which
are already IP-encapsulated?
Slightly more reasonably, we could have the tunnel driver go through the IPIP
headers one by one until it reaches the real IP packet in the middle, and
refuse to package it if it has ever been sent out by this tunnel device.

-- 
David Woodhouse,	CB3 9AN		http://dwmw2.robinson.cam.ac.uk/
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