I've been looking at the network traffic and noticed a lot of calls from one machine to an address I'd never heard of: all-systems.mcast.net

Screen Shot 2015-11-16 at 00.59.42

Information on this seemed somewhat sketchy until I spotted this page on Multicast Addresses

ALL-SYSTEMS.MCAST.NET
224.0.0.1 All systems on the local subnet.

What? All the machines on my local network? Really?

Pinging it confirmed this:


$ ping all-systems.mcast.net
PING all-systems.mcast.net (224.0.0.1): 56 data bytes
64 bytes from 192.168.1.136: icmp_seq=0 ttl=64 time=0.103 ms
64 bytes from 192.168.1.153: icmp_seq=0 ttl=64 time=14.788 ms
64 bytes from 192.168.1.120: icmp_seq=0 ttl=64 time=239.376 ms
64 bytes from 192.168.1.162: icmp_seq=0 ttl=64 time=256.191 ms
...
64 bytes from 192.168.1.119: icmp_seq=1 ttl=64 time=50.762 ms

The machine accessing all-systems.mcast.net is running a DLNA server, so it appears to be broadcasting its presence to all the machines on the local network. Panic over.