VLANs and routing

David DeSimone fox at verio.net
Fri Jun 15 16:45:17 UTC 2007

Hash: SHA1

Peter Jeremy <peterjeremy at optushome.com.au> wrote:
> > But the (somewhat weird) requirements are that the vlan interface on
> > machine1 shouldn't have assigned IP address, but the second one
> > should.
> [...]
> > Is this kind of setup even supported?
> I don't see how it could be if machine1 is an IP endpoint:  In order
> to transmit a packet, it needs to put a source IP address into the
> packet - which virtually always comes from the interface.

When originating a packet, that is the case.  But a forwarded packet
already has a source address, which can be left unchanged.  As long as
routing is working (ARP is not needed, destination is clear, etc), the
intermediate interface need not have an IP.

- -- 
David DeSimone == Network Admin == fox at verio.net
  "It took me fifteen years to discover that I had no
   talent for writing, but I couldn't give it up because
   by that time I was too famous.  -- Robert Benchley
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