[Dnsmasq-discuss] The same address on mulitple interface issue (yet again)...

Simon Kelley simon at thekelleys.org.uk
Thu Sep 25 12:02:30 BST 2008


John Gray wrote:
> I'd really like to see an option that'll allow static addresses to work
> on multiple interfaces without mucking with the machine to fiddle with
> their client id.
> 
> On a large network, fiddling with machines instead of tweaking the dhcp
> server doesn't seem like the way to do.
> 
> I realize this sort of violates the protocol.  I was thinking just an
> option, that's off by default, that allow the multiple definitions for
> the same IP.  If I request comes in for a static, we honor the request,
> and probably remove the old leases (I realize the old client won't
> necessarily know this) The option should probably have a big warning on it.
> 
> ISC allows this.  I can't tell you exactly how they implement it (I
> suspect they simply give out two leases).
> 
> I work on one network where this behavior is a requirement.
> 
> Thanks,
> John
> 

How about this as a solution?

Allow more than one MAC address in a dhcp-host statement, so that it's 
possible to specify all the possible MAC addresses that a IP can be 
assigned to.

If a MAC address asks for an IP address which is already in use, and the 
IP address is leased to one of the other MAC addresses specified, allow 
take-over.

This has the advantage that it doesn't change the behaviour of any 
currently-legal configuration, and it makes the intention  of 
newly-possible configurations explicit.

dhcp-host=1.2.3.4,<MAC of interface 1>,<MAC of interface 2>


Implementing this should be fairly straightforward.

Cheers,

Simon.





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