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I have a network of elementary Loki (Ubuntu 16.04) computers at home which work great and can be accessed over mDNS/Avahi. ping juggernaut.local works as expected, and I can reach hosts both ways over mDNS.

I am the proud holder of three work laptops, one elementary Loki, the other two macOS. I'm using Synergy with TLS between them so I can control them all with one logical keyboard and mouse.

mDNS/Avahi don't appear to be working within the network I'm currently in, as I can't reach *.local between the laptops, which are named sardaukar and arrakis. I can reach the DNS names locally with ping $(hostname).local.

Is there a guide or some series of steps I can follow to diagnose why mDNS/Avahi isn't working? Are there firewall rules I need to allow? On my home network with Linux machines, it works without issues. I'd like to get it working here so that with Synergy, I can avoid specifying IP addresses directly and rather use the mDNS host names.

  • Can you please clarify: the juggernaut.local works in your home LAN, but the sardaukar.local and arrakis.local are hosts in your workplace LAN, where these names do not work for network connectivity? – Kurt Pfeifle Dec 24 '18 at 23:48
  • They are always on the same network when I use them, things work on the home network and don't on the work network. – Naftuli Kay Dec 25 '18 at 4:12
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For .local domains to work, the mDNS protocol ('multicast DNS') is applied. This protocol is specified in RFC6762. It serves to resolve hostnames without a central DNS server, and it works through port 5353 (as compared to port 53 for DNS with a central name server).

It could be that the admins of your workplace network did setup in a way (maybe through virtual LANs, routers and firewall settings) which blocks mDNS traffic and doesn't allow to reach port 5353.

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