Date: Tue, 07 Sep 1999 15:17:05 -0400 From: Mitch Collinsworth <mkc@Graphics.Cornell.EDU> To: "Mark Jones" <mjones@mco.net> Cc: freebsd-questions@freebsd.org Subject: Re: multi-homed Message-ID: <199909071917.AA233231825@broccoli.graphics.cornell.edu> In-Reply-To: Your message of "Tue, 07 Sep 1999 13:56:05 EDT." <021101bef95a$41996f60$96baa7d1@zigzag.mco.net>
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I guess there's little point trying to reason with logic like that. I just know that if I were paying the cost of a 2nd T1 so that I could stay on the air when the first one went down, I would want to be sure that when one T1 went down all my traffic failed over to the other. But hey if it works for you, great. Remind me not to buy web service from your company. Anyhow, to answer your original question... Option A is not how IP works. At each hop, the path taken by a packet is based on it's destination address and that host's or router's current routing tables. There is no decision point based on the route taken in the opposite direction. Your reply path will be based on the destination address and the routing table at each hop along the way, including your web server. Option B is done all the time. Just point your web server's default route at your router and let the router make the decision which way to send it based on which link is up at the time. -Mitch >I know its not a perfect solution but if you look at what we had before 50% >is better then 100%. And the if you think about it quite often when you try >to access a website it will time out on the first try so when you try again >it hits the other server and comes up potentialy droping down time to 25 %. > >-----Original Message----- >From: Mitch Collinsworth <mkc@Graphics.Cornell.EDU> >To: Mark Jones <mjones@mco.net> >Cc: freebsd-questions@freebsd.org <freebsd-questions@freebsd.org> >Date: September 7, 1999 1:46 PM >Subject: Re: multi-homed > > >> >>Ok, but what about my 2nd question: about round-robin during a T1 outage? >>Have you thought about this? Unless the round-robin feature is smart >>enough to detect the T1 outage and only give out the good address while >>the other one is down, you will still lose 50% of your hits. Is this >>the elimination of downtime you were after? >> >>-Mitch >> >> >>>That would be great if they would take the fastest route. The main reason >we >>>want this is to help eliminate downtime if one t1 goes down. >>>-----Original Message----- >>>From: Mitch Collinsworth <mkc@Graphics.Cornell.EDU> >>>To: Mark Jones <mjones@mco.net> >>>Cc: freebsd-questions@FreeBSD.ORG <freebsd-questions@FreeBSD.ORG> >>>Date: September 7, 1999 1:08 PM >>>Subject: Re: multi-homed >>> >>> >>>> >>>>This is not the answer to the question you asked, but why wouldn't you >>>>want your packets to take the best/fastest/shortest path, rather than the >>>>one that came up heads this time even if it's much farther/slower than >>>>the other? I don't know if you're aware but the difference can be orders >>>>of magnitude in some cases. >>>> >>>>Also if your dns is doing a 50/50 round-robin between addresses on >>>>different providers, does this mean that when one T1 goes down half of >>>>your web hits will arrive at the server ok while the other half fail >>>>(at the browser end) due to network unreachable? >>>> >>>>-Mitch >>>> >>>> >>>>> We have two T1's one sprint one uu-net. I have configured a >webserver >>>>>machine with one ethernet card to have two ip addresses, one on the >sprint >>>>>feed and one on the uu-net feed. The default route is set to the uu-net >>>>>feed. I have set our dns to round robin the hostname between the two ip >>>>>addresses. >>>>> >>>>>When some one trys to access the server the rodrobin 50/50 between the >two >>>>>addresses no problem but the reply goes out the default route (the >uu-net >>>>>feed). >>>>> >>>>>I am looking for two options here. >>>>>A) if the request comes in on one feed the reply goes out the same. >>>>>B) it uses the default route unless that feed is down then it switches >to >>>>>the other feed. >>>>> >>>>>I think routed will do it but have no clue as to how. Going full >>>multihomed >>>>>with bgp etc is not an option. >>>>> >>>>>Any help would be appreciated. >>>>> >>>>>Mark Jones >>>>>Technical Services Manager >>>>> >>>>> >>>>> >>>>> >>>>> >>>>>To Unsubscribe: send mail to majordomo@FreeBSD.org >>>>>with "unsubscribe freebsd-questions" in the body of the message >>>> >>>> >>>> >>>> >>>> >>>>To Unsubscribe: send mail to majordomo@FreeBSD.org >>>>with "unsubscribe freebsd-questions" in the body of the message >>>> >>> >> >> >> >> > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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