I don’t think its a bug, but its definitely annoying. When I have a gateway with no reverse DNS entry (PTR record), then mdns4 blocks lookups and slows things down quite a bit.

The fix is to create a real reverse dns record, but its also possible to simply remove mdns4 and mdns_minimal from /etc/nsswitch.conf.

https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/94940