How do I route IPv4 encapsulated packets?

[Pekka Savola]

On Thu, 17 May 2001, Chuck Yerkes wrote:
[snip]
> I have the (netgear) NAT box forwarding EVERYTHING to this
> OpenBSD box (firewalls are moot when the inside machines are
> all secure).
>
> My question is this:
> What do tunnelled IPv6 over IPv4 packets look like to the
> intermediate machine?
>
> An ICMP6 packet looks like ICMP4 with more payload?

No.  When tunneling, the only thing your NAT box sees are IPv4
encapsulated packets (protocol 41).  I'd be surprised if your NAT box
managed to rewrite that, but you never know.

> Tcpdump doesn't help cause ALL the machines speak IPv6 and
> it just tells me it's an encapsulated IP6 packet.

Yeah, that's a problem with tcpdump-3.6 with ipv6 enabled.  If you disable
ipv6, you will be able to see what the encapsulating ipv4 packets look
like.

-- 
Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords