two interfaces one subnet

Chris Adams cmadams at hiwaay.net
Mon May 11 18:29:08 CDT 2009


Once upon a time, Kevin Oberman <oberman at es.net> said:
> > From: Chris Meidinger <cmeidinger at 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).

-- 
Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.




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