[114461] in North American Network Operators' Group
Re: two interfaces one subnet
daemon@ATHENA.MIT.EDU (Kevin Oberman)
Mon May 11 19:48:06 2009
To: Chris Adams <cmadams@hiwaay.net>
In-reply-to: Your message of "Mon, 11 May 2009 18:29:08 CDT."
<20090511232908.GB622256@hiwaay.net>
Date: Mon, 11 May 2009 16:47:50 -0700
From: "Kevin Oberman" <oberman@es.net>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
> Date: Mon, 11 May 2009 18:29:08 -0500
> From: Chris Adams <cmadams@hiwaay.net>
>
> Once upon a time, Kevin Oberman <oberman@es.net> said:
> > > From: Chris Meidinger <cmeidinger@sendmail.com>
> > > For example, eth0 is 10.0.0.1/24 and eth1 is 10.0.0.2/24, nothing like
> > > bonding going on. The customers usually have the idea of running one
> > > interface for administration and another for production (which is a
> > > _good_ idea) but they want to do it in the same subnet (not such a
> > > good idea...)
> >
> > This will not work right. One interface can be 10.0.0.1/24, but any
> > added interfaces would need to be /32 (10.0.0.2/32).
>
> I don't know which OS(es) you are using, but that's not true in Linux.
> I see this all the time at home; if I plug my notebook into the wired
> LAN and still have the wireless enabled, both will get an IP (in the
> same subnet) from DHCP. The wired link is the preferred default route
> by default, but you can easily set up routes for some networks via the
> wireless link.
>
> You can also set up multipath routing to send packets out both links. I
> think you can also use IP policy routing to control the choice of
> outbound interface by rule (e.g. based on source address).
This is true if you are using the WPA supplicant. It does a bit of
magic. (You can do the magic by hand without the supplicant, but it is a
pain or was the last time I tried.)
--
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net Phone: +1 510 486-8634
Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751
