1999-03-19-23:05:48 Rob Windsor:
You only have one "default gateway".
That statement may well be true for e.g. NetApps running some particular version of OnTap, and I know it's true for SunOS 4.x, but it is not a universal truth; in particular, you can usefully have multiple default gateways under Solaris 2; I believe it round-robins packets among them.
At a previous job, we had a truly sexy network set up. Had a pair of sweaty, steaming 7513s or thereabouts as the core routers for the main office; all the main nets in that office were all served by both routers, backing each other up in HSRP config. More precisely, there were two HSRP groups, one that used one router as primary and one with the other router primary. For SunOS, we spread the hosts out by hand; they'd use one or the other of the HSRP groups according to the last quad of their IP addr was even or odd. For Solaris 2 we could just list both ip addresses, for both HSRP groups, in /etc/defaultrouter and the clients would spread themselves over the two groups.
We still tried to avoid having to route packets; where we could, we tried to place the server and the clients on the same subnet, preferably on the same switch (to avoid an ISL hop). But we could soak up one heck of a lot of traffic pouring between nets:-).
Those 7513s were fun. I remember when we got 'em in, we needed to unplug our Cray to free up some amps on the UPS. Turns out a pair of fairly-well-populated 7513s do nearly as good a job of turning kilowatts into BTUs as a Cray Y/MP.
Back on the topic of multiple default routes, I'm not convinced that the advantages are worth any complexity to implement; it was pretty minor. But if it isn't hard to implement, it's kind of nice, in much the same way a round-robin Etherchannel load spreader would be nicer than a hashed-macs one; it lets a single host spread its traffic, which means that neither router normally sees as nasty of bursts.
-Bennett