FC1 multiple ethernet interface issue

[Jeff Vian]

On Tue, 2005-02-15 at 14:39 -0500, David Benigni wrote:
> >>> rchiodin at bellsouth.net 2/15/2005 11:35:01 AM >>>
> >
> > I suspect that the moving of the default route to eth1 and the
> removing
> > of the default route when eth1 is taken down has to do with the
> lookup
> > of the subnet associated with the router and the interface.  The
> default
> > route disappears because the interface with the router's subnet goes
> > down.  The matching algorithm does not take into account that there
> is
> > another interface on the same subnet.  It might be a bug, but most
> > systems are not configured with two interfaces in the same subnet
> > without some sort of bonding or bridging.
> 
> This wouldn't be the first time I'm doing something that is out of the
> norm :)
> 
> > I've tried to sort out Dave's posting (fix your email client to not
> > create a new email thread for each response) and conclude that there
> is
> >one particular host he wants to communicate with on one of the
> >interfaces and everyone else on the other.  Why, and is this host
> >directly connected?  It might be easier to burn a private subnet for
> >this one host and let linux be it's default gateway (NAT and ip
> >forwarding).
> 
> Sorry about the email client, I'm pretty much stuck thought (Novell
> GroupWise).  
> 
> Hears the story of what I'm trying to do.  This box runs DHCPd and
> bind.  For legacy reasons, I have to bind multiple
> ips to the box for an unknown amount of machines that are hard coded to
> the old ip address.  So, initial (and possibly
> flawed) though was to have the new ip I want to roll out 10.x.y.107
> bound to eth0 and bind 10.x.y.114 to eth1.
> Then when all the legacy systems are fixed, I can easily just down
> eth1.  I'd rather mess with eth1 since its not so
> critical as eth0. 
> 
> So, thats the situation.  Any ideas are welcomed. 
> 

Now that you have explained that, it may be simpler to use another IP
address as an alias on eth0

for example
eth0     10.x.y.107
eth0.1   10.x.y.114

Now all traffic for that subnet goes thru the same interface. you can do
an ifdown on eth0:1 without affecting the traffic on eth0 and without
having the gateway change on you.


> Thanks,
> Dave
>