mDNS works once, and then fails

I have freshly installed OpenWRT onto a Linksys E8450. For some reason, mDNS (Avahi) is failing. If I ping the .local domain for one device, the ping will succeed, but then if I try to ping it again it will say "Destination unreachable: No route". Other devices are simply unreachable via mDNS. On a previous installation of OpenWRT on the same device, mDNS worked fine. I'm not sure what is different.

I rebooted the other devices on the network, then mDNS started working. I'm not sure exactly what the problem was — perhaps some table needed to be forced flushed since the new router was connected.