On Wed, Mar 21, 2012 at 12:44 PM, Worley, Dale R (Dale) <dworley@xxxxxxxxx> wrote: > OK, I know nothing about the subject, but when I do "ifconfig" I get: > > eth0 Link encap:Ethernet HWaddr 00:16:35:AF:82:03 > inet addr:135.55.22.90 Bcast:135.55.22.255 Mask:255.255.255.0 > inet6 addr: fe80::216:35ff:feaf:8203/64 Scope:Link > UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 > [...] > > Looking at the link-local address, it appears to be constructed from > the interface's MAC address, and basically nothing else. > > This suggests that the link-local address of another system on an > attached network would contain that system's MAC address, but nothing > to identify which network, and thus, *this* system has no algorithmic > way to determine which interface goes to the proper network. You've just rediscovered what the "link local" part of the link-local address means: the address is local to the link! It is not globally unique or even unique within a host, it is just unique within a link. Thus, if a host has more than one interface (and most do: at least one network interface + loopback, which is a separate interface), you need to tell it which one you mean when you use link-local addresses. -- Craig A. Finseth