I have seen routers send packets with a source ip in the 10.x.x.x range. The IP type of 89 (it's not a port number, see post #4) and the multicast address of 224.0.0.5 point to a router using OSPF.

If you had a packet capture we could confirm that. (since packets sent to 224.0.0.5 should have a TTL of 1 because they should not be routed beyond the router their sent to.)