Routing issue

[Matthew Seaman]

On Mon, Jul 19, 2004 at 12:55:45PM -0500, Web Walrus (Robert Wall) wrote:
> > > > > ifconfig_dc0 inet 1.2.3.4 netmask 255.255.255.248
> > > > > ifconfig_dc0_alias0 inet 2.3.4.5 netmask 255.255.255.248
> > > > > defaultrouter="1.2.3.1"
> > >
> > > It's not on the same network; that's the problem.  Two complete separate
> > > networks, same interface card.  The issue is that one of the networks
> > > works, and the other doesn't, depending on what network the default router
> > > happens to be on.
> >
> > In general, you're going to need a mechanism for dynamically routing
> > packets in order to make this sort of setup work.  For most setups,
> > you'ld need the co-operation of your ISP to make things work as well.
> 
> The situation is this - there are 4 servers that are on one network.  I'm
> trying to switch them over to another network, but I need to do it without
> downtime.  Therefore, I need to have both IPs completely active and
> functional simultaneously.

Right -- in which case, you've actually done everything right,

> Is there any way to determine what IP/interface a connection came in on,
> and continue to use that IP/interface for the outbound packets?  Maybe
> with static routes or something of that nature?

That should happen automatically whenever anyone connects to one or
other of those addresses.  It's setting the origin address on outgoing
connections that's usually the difficult bit, but in this case, that
shouldn't be a problem.  Really all you need to do is at some point
change the default route to point to the new gateway, and then wait
until any traffic to the old addressess dies away.  Then edit
/etc/rc.conf to make the new ip address the only one configured on the
interface and whatever else needs fiddling with similarly, a quick
reboot and you're done.

	Cheers

	Matthew


-- 
Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP: http://www.infracaninophile.co.uk/pgpkey         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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