[Dnsmasq-discuss] Test release with tag-if support (was IP address based on switch port number (option 82))

[Simon Kelley]

richardvoigt at gmail.com wrote:
> Resending this e-mail because it's very relevant to the broken
> behavior noted by Ignacio in the test release.
> 
>>> Ignacio, why not configure you switch to relay all ports? Then you can
>>> block broadcasts without problems. You don't have to have special
>>> configuration in dnsmasq for all the ports, it will do boring dynamic
>>> address allocation fine on relayed requests. (Remember that the netmask
>>> is not option in dhcp-range lines used by clients behind a relay.)
>>>
>>> Michael: the change I was thinking of should be completely transparent
>>> in all other situations except this. It just inhibits filtering of
>>> available dhcp-ranges by tag on a unicast DHCP renewal. Since by that
>>> time a lease will exist and the address is known, at most one dhcp-range
>>> can match anyway.
> 
> I don't think this is a solution.  If you moved a station between
> ports, it would renew the address assigned to the old port, which both
> doesn't meet the OP's stated requirement and leaves the next device
> connected to the old port with no available address.
> 

True, but if it's not possible to arrange for the relay to behave as a 
full proxy, there's no choice, since there's no way to make unicast 
renewals work.

In the absence of server-id-override support in the relay, it might be 
possible to implement it wholly in the server: the server-id code could 
be configure to always use the address of the relay as server-id, and 
get the same effect.

If that works, there would be no need for modified behaviour on unicast 
renewal.

Cheers,

Simon.