Router Asus RT-AC51U, OpenWrt 23.05.0 . Configured with WAN, LAN and a single (for now) WiFi network. LAN and Wifi have a different subnet. Firewall set up to forward LAN to WAN and Wifi, and Wifi to LAN and WAN. A smartphone in wifi works fine, termux can ping wan sites and PCs on the LAN. From a LAN PC, ssh to the router, then running umdns shows devices on the lan. So far, so good.
On the Wifi is a printer with a fixed IP address in the correct subnet, outside DHCP range. I can ping this printer from within the router, and from the smartphone with termux in the same wifi. This printer (also) uses Bonjour/ZeroConf to announce itself, tcpdump on the wifi interface shows broadcasts to mdns.mcast.net.5353 . I can force the broadcasts by switching the Bonjour feature off, then on in the printer. But umnds does not show this printer. Neither can PCs on the lan discover the printer.
Why does this fail? Should there be special firewall rules for Bonjour (UDP port 5353) ?
It seems mdns does not work across different subnets. I can get a WiFi attached printer working by specifying its direct IP address and the proper port (9100), but the scanner in the printer does not work via the network.
Is there a way to make mdns announcement coming in from one subnet be announced on other subnets? From reading the manual, the igmp proxy is for something else.
Thanks for any pointers, Mat
Thanks for the quick reply, a useful link. Doesn ´t umdns not offer that? I have configured /etc/config/umdns with a "list network xxx" line for each of the three networks I want to have this working. An "ubus call umdns update", then an "ubus call umdns browse" shows devices on two of the networks, so the router picks it up. If I do a "avahi-browse -a" on one of the configured networks, none of the data that the router knows shows up.
I will try igmpproxy, and see I I can disabled it for all but the desired networks 9no wan, for instance)
It mostly works now using Avahi, thanks for the link. The link contains some outdated info, now the package is called avahi-daemon-service-ssh , and does not use dbus.
I have limited this to the family networks, the guests and IOT wlan networks cannot use it (tested it too!)
Doing "avahi-browse -a" on PCs on the family network shows the devices, and importantly the document scanner now finds the printer/scanner. One remaining issue is that a PC connected directly to the router does not see the devices, while those after a switch do (and the switch is attached to the router).