As one approach to seeing whether a group of routers were acting correctly, I wrote some code to trace all possible routings in a network. The basic approach was to gather (via SNMP) all the routing tables of all the routers (SNMPv2 GetBulk could help keep this reasonable) and run through the routes for each subscriber net to every other subscriber net. This presumed a backbone set of routers and a known set of networks behind each "POP" router. The program took less than a second on a Sparc ELC, for 30+ routers and 100+ subscriber nets. The program highlighted long routes, loops (such as when defaults point to defaults that point back...), and dead ends. The diameter of the network was settable and "long" was defined as some amount above the diameter. The intent was to discover that "reasonable" routing was happening...there was no intent to insist on optimal routing. The snapshot of routing tables could be a blurred one, as dynamic routing protocols could be changing routing tables during the period of table collection. The same effect could be achieved by doing "traceroutes" from every subscriber network, but this gets messy. Overall, it was a fun exercise and the operational requirement was that you identify where each network attached to your backbone. Then you look at actual routing tables to see that your routing protocols were being reasonable about service. The program has been packaged and is available online: ftp://aelred-3.ie.org/pub/chkrtr.tar Enjoy and let me know any reactions to the scheme. Walt