I didn't see the start of this thread, but here's my $0.02 ...
The DHCP server shouldn't care what interface the request came in on, rather it looks at the source network of the request.
So you server could support many different ranges, provided there was suitable separation (i.e. a router) between the subnets and the server.
In your case, the server is acting as the router, but having separate interfaces on the server itself is not a requirement (of any DHCP server I know of)
regards, Matt.
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