Date: Sat, 17 Mar 2001 12:31:46 -0500 (EST) From: Alex Pilosov <alex@acecape.com> To: Nick Rogness <nick@rogness.net> Cc: freebsd-net@FreeBSD.ORG, Jeroen Ruigrok/Asmodai <asmodai@wxs.nl> Subject: Re: same interface Route Cache Message-ID: <Pine.BSO.4.10.10103171216120.8329-100000@spider.pilosoft.com> In-Reply-To: <Pine.BSF.4.21.0103171047250.16998-100000@cody.jharris.com>
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On Sat, 17 Mar 2001, Nick Rogness wrote: > There is no way to tell your packet to go back out to ISP #2. That is the > point I'm trying to get across. Unless your running a routing > daemon. But is that really practical with cable modems, dsl, etc?...I > don't think so. <flame> Is the clue really gone from this list? </flame> Now, correcting glaring mistakes of the above two posters: a) Multihomed means having two connections to public Internet b) route-cache means fast lookup of destination gateway. Lookup of destination gateway may be slow (see d), and it makes sense to keep track of a TCP connection and 'fast-switch' (cisco lingo) the following packets, caching the following data (destination, ACL list) from the first packet. Usually route-cache is implemented in hardware in ASICs, but sometimes it may make sense to implement it in software (when overhead of connection tracking is less than overhead of route/acl lookup). Route-cache has nothing to do with policy routing (d) c) Running routing daemons has, once again, nothing to do with policy routing. It only means you are consensually exchanging routes with your neighbours. IF you are big enough to run BGP4 to your upstreams, you need to run routing daemon (gated/zebra/etc), and you are not likely to have need for policy routing, because your IPs are all equal: all networks you have can(will?) be delivered (and can be sent over) over any interface that you have. d) Policy routing is a generic term for any sort of routing (i.e. choosing of destination gateway for a packet) that is not exclusively based on destination IP address. It may be based on src/dest port, TOS field, source IP address, etc. FreeBSD has no support of that, to my knowledge. Linux has something called 'iproute2' which does support it, by having multiple routing tables, and a ruleset that decides which routing table to use based on packet details. With policy routing, you indeed will be able to multihome, without any cooperation of your upstream (assuming strict filters on their ingress interfaces) and have things work. -- -- Alex Pilosov | http://www.acecape.com/dsl CTO - Acecape, Inc. | AceDSL:The best ADSL in Bell Atlantic area 325 W 38 St. Suite 1005 | (Stealth Marketing Works! :) New York, NY 10018 | To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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