From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rene Gallati Date: Thu, 20 Jan 2005 07:25:20 +0000 Subject: Re: [LARTC] Interface not marked down when links are down Message-Id: <41EF5CE0.2040501@draxinusom.ch> List-Id: References: <20050120020957.43586.qmail@web50108.mail.yahoo.com> In-Reply-To: <20050120020957.43586.qmail@web50108.mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable To: lartc@vger.kernel.org SPJ wrote: > I am not sure if this problem has already being > posted, but I haven't found any solution. Excuse me if > it's a repost but would appreciate any pointers.=20 > I have newly configured Multipath default route. I > have 1 local connection and 4 internet connections. I > am using kernel 2.6.7 and have applied Julian's > relevent patches.=20 > When the next hop is down, julian's patch takes care > of the links changing the route to only the links > which it finds are up and forwarding traffic to those > links. But if the problem is anywhere in between, > beyond the next hop, the links are not marked > identified as down (I down see the change in multipath > default route) and requests still go via them and > hence no connectivity, even if some other links are > up. > Does Julian's patch takes care of route only if next > hop is down. Any solution to this problem? You are looking at the wrong layer. If the next hop is unreachable,=20 which is a layer 2 thing, the system notices this and acts accordingly.=20 If however a link further away is down, there is no such mechanism on=20 layer 2 and your system cannot react to it (with standard means). This is quite "psychic" if you want. Why should your system magically=20 know there is a problem 4 hops upstream ? It only sees the links it is=20 directly attached. The packets are accepted on one link and this is=20 where the responsibility of your multihomed system ends. It neither does=20 nor should track packets over the full path from source to destination. There is a solution however: For that kind of thing you need to look=20 into routing software (BGP, OSPF) which has this capability. If you=20 don't control the upstream machines, you will need to get a bgp-peering=20 with your upstream provider to be able to react to outages. If your=20 mentioned 4 connections are standard home-adsl/cable connections, this=20 might be difficult however. Hope that helps. --=20 C U - -- ---- ----- -----/\/ Ren=E9 Gallati \/\---- ----- --- -- - _______________________________________________ LARTC mailing list / LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://lartc.org/