On Sun, 7 Apr 2002, Richard A Steenbergen wrote:
> Layer 3 devices usually do a form a load balancing called "equal cost" > forwarding. If you have two routes to a single prefix (say you have two > physical links), and both have the same routing "cost", packets may be > load balanced across those links. Some mechanisms (for example Cisco CEF) > can do this on a per-destination (flow-based) basis, to prevent packet > reordering. I seem to remember fast switching was per-destination, and CEF was round robin. But it seems CEF is now per-destination as well in IOS 12.2. Round robin is optional. > But some protocols can't support this, for example UDP or ICMP > traceroutes usually don't get grouped into a "flow", so you can see this > kind of load balancing in practice on the internet when you get back > traceroute answers from different probes on the same hop. Routers usually don't really take full flow information into account, but only look at the destination IP address or do a hash over some fields. So usually traceroute doesn't behave differently from regular traffic. This link answers the original question for another router vendor: http://www.juniper.net/techpubs/software/junos51/swconfig51-policy/html/policy-actions-config10.html#1015470
