Date: Sat, 28 Apr 2001 23:37:44 -0700 From: "Ted Mittelstaedt" <tedm@toybox.placo.com> To: "Ken Bolingbroke" <hacker@bolingbroke.com>, <questions@FreeBSD.ORG> Subject: RE: Redundant Internet connections Message-ID: <015b01c0d076$e5e544a0$1401a8c0@tedm.placo.com> In-Reply-To: <Pine.BSF.4.21.0104281651400.87921-100000@fremont.bolingbroke.com>
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>-----Original Message----- >From: owner-freebsd-questions@FreeBSD.ORG >[mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Ken Bolingbroke >Sent: Saturday, April 28, 2001 5:08 PM >To: questions@FreeBSD.ORG >Subject: Redundant Internet connections > > > >Given a FreeBSD box with _two_ independent connections to the internet, >and also serving as the gateway to a third, private network, how would I >configure it to use both Internet links as "default" routes? You don't. The concept of a "default route" always mandates that on a single host that a SINGLE connection exists to "The Internet" I would >prefer one over the other, but need it to fall back to the second if the >first goes offline. > In this case the "preferred" route _is_ the "default route" and the "non-preferred" route is _not_ the "default route". In the event that the default route goes offline, then what you apparently want to have happen is that this route _stops_ being the default route, and the non-preferred route _starts_ being the default route. You may think all this is semantics, but it's a very important concept in Internet routing - because the default route mandates ALL traffic pass through it that is not explicitly routed elsewhere. Since there are nearly a hundred thousand routes on the Internet, for typical Internet traffic from a typical going concern there is not a snowball's chance your going to be able to get any kind of "load sharing" going using default routing in this scenario. In short, ALL your _inbound_and_outbound_ traffic will _always_ come through _one_ of the multiple links you have set up, as long as you are using default routing. Now, if you don't like this idea, and your thinking that you can have, say, 70% of the traffic go in and out the preferred route, and 30% go in and out the non-preferred route unless the preferred route dies then you have 100% go in and out the non-preferred route, then the only way that you can do it with multiple ISP's is to obtain an AS number, and do BGP with both ISP's. Generally, you can't get AS numbers unless you have a valid business justification, and a single FreeBSD system on 2 DSL lines (if this is what you have running) ain't it! But, if you have the money to spend on multiple ISP connections that duplicate each other and you don't care that 99% of the time one of the pipes is going to be wasted, why then you can implement this kind of "default route switching" if you want, there's a number of ways to do it. >I would have thought routed would do this, but I can't see any indication >that it does redundant links. If I'm wrong, please point me at an example >configuration, or alternatively anything else I can use to accomplish >this. > routed runs the RIP protocol and that does redundant links just fine - given the proper network setup. As a matter of fact I just published a "poor man's redundancy" solution using routed and RIP on FreeBSD to set up a V90 redundant backup line for a DSL line. You can read it at http://www.computerbits.com in the Network Community section. However, you WILL NOT be able to do this with multiple ISP's, don't even waste time trying. You need to give some more background, like what kind of links and so on, that you have before anyone could assist here. But, I can tell you that I have a feeling that I know what your trying to accomplish and I also have a feeling that you don't understand all of the ramifications of why it won't work for most applications. I also think that for the few apps that it would work for, that your going to have to have an awful icky hack on that FreeBSD system. My advice here is this: In Internet Connectivity, people assume that "cheap unreliable high-speed ISP connection" + "cheap unreliable high-speed ISP connection" = "reliable cheap high-speed connection" However, this is wrong. There is no such beast as a CHEAP reliable high-speed connection. The three don't mix. If you need high-speed reliability, pay the money for it. If you can't afford it, then either make do with high-speed unreliability, or low-speed reliability. Ted Mittelstaedt tedm@toybox.placo.com Author of: The FreeBSD Corporate Networker's Guide Book website: http://www.freebsd-corp-net-guide.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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