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Date: Thu, 14 Aug 2008 16:24:56 -0400 From: Vlad Yasevich <vladislav.yasevich@...com> To: Pekka Savola <pekkas@...core.fi> Cc: netdev@...r.kernel.org Subject: Re: interface down: v6/v4 address deletion difference Pekka Savola wrote: > Hi, > > I recall there was discussion about this a couple of years back, but I > couldn't find it for all I could try. > > There seems to be a difference in how v4/v6 addresses are handled when > interface goes down (manually added addresses are gone forever > regardless of whether it's tentative or nor; link local address is > deleted but reappears when link is back). > > Example on 2.6.25.10-86.fc9 using pan0 interface (just because it's > easiest to play with it): > > # ip l set up dev pan > # ip a a 10.0.0.1/24 dev pan0 > # ip -6 a a 2001::1/64 dev pan0 > # ip a l dev pan0 > 8: pan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state > UNKNOWN > link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff > inet 10.0.0.1/24 scope global pan0 > inet6 2001::1/64 scope global > valid_lft forever preferred_lft forever > inet6 fe80::34ca:62ff:fe2a:717b/64 scope link > valid_lft forever preferred_lft forever > # ip l set down dev pan0 > # ip a l dev pan0 > 8: pan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noqueue state DOWN > link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff > inet 10.0.0.1/24 scope global pan0 > # ip l set up dev pan0 > # ip a l dev pan0 > 8: pan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state > UNKNOWN > link/ether 36:ca:62:2a:71:7b brd ff:ff:ff:ff:ff:ff > inet 10.0.0.1/24 scope global pan0 > inet6 fe80::34ca:62ff:fe2a:717b/64 scope link tentative > valid_lft forever preferred_lft forever > (and after a while 'tentative' flag goes away) > > Shouldn't behaviour be consistent across v4/v6? > >From what I remember explained to me, this is due to different host models of operation between IPv4 and IPv6 in linux. IPv4 is implemented using a weak host mode, while IPv6 is a strong host model. So, when the interface is brought down, all IPv6 addresses are removed since Linux considers them assigned to the interface and not the host. -vlad -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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