arp-proxy

[Brian Candler]

On Thu, Nov 10, 2005 at 02:25:07PM +0100, Jon Otterholm wrote:
> In all this - our role is similar to an ISP, but we are buying access to
> our customers from an external part. Every customer is delivered on a
> separate vlan trunked. 
> 
> - Our DSL customers cannot be set on the same VLAN i a single DSLAM
> (don't ask me why - ask Alcatel).
> - We cannot build a simple bridge because the Network service provider
> can't handle when a MAC-address shows up on 2 different VLAN's.
> 
> The arp-proxy should do the following:
> - Forward any broadcast packets but rewrite src to its own mac.
> - Forward unicast packets according to FDB but rewrite src to its own
> mac.

Can you not perform normal routing - that is, allocate a separate IP subnet
to each VLAN? This uses some more IPs than a 'flat' addressing space, but
it's guaranteed to work properly.

If your DSL traffic is presented as PPPoE, maybe you can get away with just
having a separate PPPoE listener on each VLAN. If it's presented as L2TP you
could use private IPs for the tunnel endpoints.

Otherwise, a bridge which rewrites source MAC addresses as packets pass
through - that's just too awful to contemplate. As you say, you'd also have
modify ARP responses to have the bogus MAC addresses too. Dealing with
multicast, IGMP, Netbios... no I really don't want to contemplate it :-)

Regards,

Brian.