I have a network set up something like the following:
Device A <---> Router A <---> Router B <---> Device B
where Router A is a tp-link Archer AX73, and Router B is a tp-link Archer C7. Router B is flashed with OpenWRT, and Router A is using stock firmware. Router B is set up to be a wireless bridge between Router A’s network, and its own (it was set up using this guide).
What I am wondering is if Device A can find, say, Device B.local, using Avahi (assuming Device A, and Device B both have Avahi installed, and running), over this bridged network. So far, I haven’t been able to get it to work, so I’m wondering if it is possible at all. I have read that Avahi only works on a local network, but I was wondering if it could be bridged.
UPDATE (2024-01-16T01:28Z):
The issues that I mentioned in this post have since been solved. The majority of the issues stemmed from the fact that the relay software that I was using, relayd, doesn’t support ipv6. All the tests that I was conducting were defaulting to ipv6, so it was appearing like the bridge was failing unpredictably. Since that realization was made, and countermeasures were enacted, the problem was solved.
Avahi uses mDNS which is a multicast protocol. Multicast is designed to be link-local only: it ends at the edge of a broadcast domain. Router A would also need to bridge in order for that to work (i.e. Device A and B would need to have the same broadcast ip).
On the other hand, there are ways of setting up Multicast Forwarding if the router supports it, or you could have a device in both networks that does Avahi/mDNS Reflection.
https://www.cisco.com/assets/sol/sb/Switches_Emulators_v2_3_5_xx/help/250/index.html#page/tesla_250_olh/multi_forwarding.html https://serverfault.com/questions/121032/forward-mdns-from-one-subnet-to-another
Why would Router A also need to be a bridge? Router B is configured to bridge its devices to Router A’s network, so, from what I understand, its devices are treated as if they are on Router A’s network – bridging is layer 2, and mDNS is layer 3 (afaik), so Avahi should be able to resolve across the bridge.
Wouldn’t this only matter if Device A, and Device B were on two separate vlan’s?