[radvd-devel-l] Advertising interface is not "autoconfigured"

Venkata Jagana radvd-devel-l@litech.org
Thu, 24 Jan 2002 12:20:39 -0800

On this very topic, Pekka and I exchanged several emails more
than 6 months ago and obiviously, there are disagreements on
whether router interfaces need to be autoconfigured or not.

According to RFC 2462, the autoconfiguration process specified
in this doc is applied to hosts but not routers and however,
there is nothing that says router interfaces can't be autoconfigured.
If they should't be autoconfigured then in manual configuration, what
prefixes would be used to configure those interfaces. Wouldn't they
be same as the prefixes advertised by radvd on the respective interfaces?

Looks to me that it is purely an implementation and startup issue.

In fact, I believe (based on old email on this topic on netdev) the
KAME stack doesn't seem to even accept or autoconfigure addresses for
router interfaces based on RA's received from other routers. But that's
not the case in radvd for Linux either. Radvd daemon on Linux is
disallowing autoconfigration with the advts from the same router but
not from other routers if forwarding is enabled and I believe this is
inconsistent. If it just cares about prefixes in the RA's, then that's
all it should build in its prefix list and ignore the autoconfiguration
part completely.


Venkata R Jagana
IBM Linux Technology Center, Beaverton
Tel: (503) 578 3430 T/L 775-3430

Pekka Savola <pekkas@netcore.fi>@litech.org on 01/21/2002 09:36:24 PM

Please respond to radvd-devel-l@litech.org

Sent by:    radvd-devel-l-admin@litech.org

To:    radvd-devel-l@litech.org
cc:    vjardin@wanadoo.fr
Subject:    Re: [radvd-devel-l] Advertising interface is not

On Mon, 21 Jan 2002, Venkata Jagana wrote:

I'm not sure why one would want to autoconfigure eth0 in this case?

> Before you run radvd on your 'R' box, turn off or disable the forwarding
> temporarily through
>    echo 0 > /proc/sys/net/ipv6/conf/<all or ethX>/forwarding
> Run radvd and then enable forwarding through
>    echo 1 > /proc/sys/net/ipv6/conf/<all or ethX>/forwarding
> This is one way of enabling autoconfiguration for router interfaces.

Changes in radvd 0.7.1 probably kill this approach (if "all") is used --
radvd will not start unless "all" forwarding is enabled.

Having conf/eth0/forwarding=0 is effectively a DoS for the clients for the
period it's 0, but in simple scenarios this may not be a problem.

Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords

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