On Fri, 14 Dec 2001 10:52:28 -0500 Adrian Chung <adrian@xxxxxxxxxxxxxxxxxx> wrote: > Actually, after I wrote my last couple of messages, I was thinking > about it more, and I think it's a misunderstanding that I have. Your > HOWTO is mainly geared towards load balancing, and failover when one > of the links goes down. > > I'd like to do that, but I'd like to mainly use one link, and only > fall back (fail over) to the second link when the first goes down. You are right, this is a quite different situation. It worked for me like that before installing Julian's patches. I had no multipath route, but explicit routes to the gateways and never more than one default route. Then I had a daemon running which ping'ed the gateways and would delete the default route to put the other. But this is loosing the bandwidth of a line which is being payed, so I was unhappy with that solution. Unfortunately, I don't know which is the best routing setup for your case. Maybe somebody else on this list can give you a hint. > My two links are through different ISP's, and I want to be able to use > both ISP's news, and proxy servers. In order to do this, I need to > make sure that when accessing ISP1's news server, I always connect via > the same link. > > Load balancing defeats this, by sometimes routing to ISP1's news > server via ISP2, and then I get denied access because I don't have a > source IP on ISP1's network. You should be able to add an explicit host route in table main. That is hit before the multipath route is queried. You do know the IP of that ISP's news server, do you? > 1) is there a way to only use the second link if and when the first > goes down, instead of load balancing via both links all the time? As I said above, the contrary was the aim of my setup. I would imagine that the solution is not using a multipath route but just two default routes with different priority. If the first is working, it should be used always; if it goes down, the second would be used. And if the first comes up again, thanks to Julian's patches, it should be used again. But note, that for this last step to work, I think you still need to ping/arping the gateways, such that there is a chance to detect that the failing link is up again. > 2) is it possible to implement source-based policy routing but fall > back to the second link when the preferred gateway is down? I think it is, using two default routes with different priority. > Does any of this make sense? Unless you have to pay for traffic on one link and not on the other, I'm not sure why you would want to leave a link unused. Beside that, I think it does make sense. -- Christoph Simon ciccio@xxxxxxxxxxxxxxx --- ^X^C q quit :q ^C end x exit ZZ ^D ? help .
