Networking basics: in princliple[*] there can only be one DHCP server per L2 broadcast domain[**]. So first thing you need to get straight is your L2 network and only after that deal with issues of your higher layers (IP is L3, DHCP is strictly speaking L2 but with hooks to L3).
[*] There can be more than one DHCP server per L2 broadcast domain, but all of them either
- work independently and it's matter of almost randomness as to which DHCP server's offer will be used by DHCP client. Not entirely randmoness, it's the answer of DHCP server which answers first. Which can be affected by network latencies and DHCP server performance.
- are configured in master/slave or multi-master configuration which means they synchronize lease data behind the scene. They both/all serve IP settings for the same IP subnet. That's a very advanced feature of DHCP servers, most of implementations don't support it.
[**] L2 broadcast domain is nowdays most commonly an ethernet network, delimited from other L2 broadcast domains by a router. Switches and bridges are parts of same L2 broadcast domain, so if you have multiple ports members of same bridge in ROS, that's still same L2 domain.
Another L2 entity is VLAN (although it's on top of another L2 entity, which is ethernet subnet), so same principles (single DHCP server) apply.
And when dealing with bridged L2 networks in ROS, the proper thing is to bind services, provided by router (everything IP-related, also DHCP server and client), to bridge
interface ... member ports should be considered as ports, not interfaces. This
article nicely explains multiple personalities of a bridge in ROS.
You probably wonder what's the difference between interface and port: interface is an entity which allows device to interact with connected device(s). Nowdays interaction is done mostly via IP, so interface allows IP configuration. Port, OTOH, is an entity which allows to connect device(s). On computer and router (in the narrow meaning), interface is almost synonymous for port as one interface is bound to exactly one port. On switch (or bridge), there are many ports members of same L2 broadcast domain, but there are no interfaces (when talking about non-managed switches). Or there can be a single interface which allows switch (or bridge) device to interact to all devices connected to ports of same switch/bridge.
When creating bridge in ROS, member ports (e.g. etherX) should not be used as interfaces any more. Although ROS does allow to use member ports as interfaces, it's still wrong.