I think this is little OT here, because the question is mostly network orie nted. However my nodes will be Linux embedded boxes and some solutions coul d be very low-level, so I think many of you could help me in some way.
I have N Ethernet hosts based on embedded Linux. Each one features an Ether net interface dedicated to the final user that could change the IP address configuration. On that interface a Web server responds. All the nodes will be configured on the same subnet and conected to a switch.
Now I need to make an "internal" communication among those hosts. With the work "internal" I mean the user should ignore the presence of this communic ation and relevant details (it should not be necessarily invisible to a tra ffic monitoring tools). For example, when the user changes the IP address of host 1, the new IP add ress shouldn't be configured in host 2 too and the internal communication b etween host 1 and 2 should continue without interruption.
I thought about three possible solution, but I'm not a netowrk guru.
The first is to add other logical IP addresses (aliases) used for internal communication only. Those IP addresses will be hardcoded and never changed by whoever. The user will be able to configure only the main IP address for each host. Is this could work with a simple switch? I think yes, because t he switch looks at the MAC address and doesn't see the IP addresses. Anyway I don't know what negative effects could be when the same broadcast domain is shared by two different subnet (internal, with hardcoded and fixe d IP addresses, and external, configurable by the user as he wants).
Another solution is to implement the internal communication staying at leve l 2, so avoiding IP addresses, but using only MAC addresses. I could invent a proprietary layer 2 protocol. This could avoid any conflict with IP addr esses customized by the user, but there are some disadvantages. How host 1 could know the MAC address of host 2 for internal communication? It could be written during delivery of the system, but replacing one host on the field could be difficult (the MAC address of replaced host should be changed on the other nodes). I could invent a proprietary broadcast ARP pr otocol (what is MAC address of **host 2**). In order to avoid the issue of knowing the MAC address of other hosts for i nternal communication, I could invent a L2 protocol made by all broadcast f rames, considering it will a low-bandwidth protocol.
The third solution is using VLANs, but I don't know if they can be useful i n my case. Indeed, I couldn't use static (port-based) VLAN, because I will have two VLANs on the same switch ports. Anyway I should have two IP addres sed on each host (as in the first solution).
Other suggestions?