From: Vlad Yasevich <vladislav.yasevich@hp.com>
To: Pekka Savola <pekkas@netcore.fi>
Cc: netdev@vger.kernel.org
Subject: Re: interface down: v6/v4 address deletion difference
Date: Thu, 14 Aug 2008 16:24:56 -0400 [thread overview]
Message-ID: <48A49498.4010601@hp.com> (raw)
In-Reply-To: <alpine.LRH.1.10.0808142017050.23001@netcore.fi>
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
prev parent reply other threads:[~2008-08-14 20:24 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-14 17:25 interface down: v6/v4 address deletion difference Pekka Savola
2008-08-14 20:24 ` Vlad Yasevich [this message]
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