IPv4 -> IPv6 "bridge" ?

Benedikt Stockebrand me at benedikt-stockebrand.de
Wed Oct 13 16:28:56 CEST 2010

Hi list,

Martin Millnert <martin at millnert.se> writes:

> There are various userspace tcp proxy programs out there (google 'tcp
> ipv6 proxy), including socat, which can accept a connection on ipv4 or
> ipv6 and forward it to a host on ipv4 or ipv6. 

just for completeness sake: Yes, this works---sort of.  I've used
socat in the past to provide Ssh/IPv6 connectivity for a handful of
IPv4-only systems for monitoring purposes.  To do so I configured an
additional (v6) address on the "proxy" machine running socat and
started socat bound to that address.  Add a AAAA record to the DNS for
that address and you're basically set.

The same should do with SNMP, but I never had a reason to try it out.

There is however a drawback involved here: socat won't translate ping,
so what you wind up with the situation that you may able to ping the
address (because the "proxy" machine answers) while the actual target
is down.  This can turn into a minor pitfall with regard to a
monitoring setup and a major nuisance if there are semi-clued users
around who know about ping/ping6 but don't fully understand this setup
(think Java developers here, for example).

So in many-clients-few-servers environments the straightforward
approach is still to make the servers dual-stacked where needed.



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