[ale] router not on the network?

Bao Ha baoh at linuxwizardry.com
Wed Jan 31 14:37:52 EST 2001



Great!  I have been waiting for this mystery to be resolved.

The router/gateway is on the same LAN, but with a different IP
subnet.  Instead of assigning an Ip alias, you just tell it to
look for the gateway on the eth0 interface.  It probably just
does an ARP and the gateway responds.

And yes!  Many networks are setup that way.  Usually, this is
where your network admin will step in.  Without additional info,
I thought that you may need RIP or some routing protocols to
discover your closest hop.

IMHO, Linux is right when refusing to allow you to add a gateway
not on the same subnet, untill it has enough information.  Windows
works since it makes certain assumptions, which may not be valid
and very difficult to debug when problems occur.

Bao

-----Original Message-----
From: owner-ale at ale.org [mailto:owner-ale at ale.org]On Behalf Of
To: ale at ale.org
hirsch at zapmedia.com
Sent: Wednesday, January 31, 2001 1:21 PM
To: Stephan Uphoff
Cc: hirsch at zapmedia.com; ale at ale.org
Subject: Re: [ale] router not on the network?


Stephan Uphoff writes:
 >
 > Try:
 > 	route add -host x.y.z.t dev eth0
 > 	route add default gw  x.y.z.t

Yow!  That did the trick.  Thanks a million.

Is this a standard network setup?  No one I've talked to has ever
heard of a setup like it.

Thanks again,

Michael

 >
 > > I recently tried to put a linux box on a network that had a
 > > configuration I'd never seen.  It was one of those "it worked fine for
 > > my Windows laptop, why doesn't it work for Linux" things.
 > >
 > > The setup:
 > >
 > > IP address: a.b.c.d
 > > netmask:    a.b.c.0
 > > gateway:    x.y.z.t
 > >
 > > So the gateway was not on the lan.  I gather there is some firewall
 > > that is doing some kind of transparent NAT on onto the internet.
 > > /sbin/route would not let me configure a gateway that can't be
 > > reached, so I was hosed.
 > >
 > > Have you ever seen this setup before?  Someone mumbled that there was
 > > a networking patch for this, but I'd never heard of it.
 > >
 > > Now Linux looks bad in this guy's eye because it can't do what Windows
 > > did.  I'm guessing that this is some MS extension to IP, but I really
 > > don't know.
 > >
 > > Thanks in advance,
 > >
 > > --
 > > ------------------------
 > > Michael D. Hirsch, Ph.D.
 > > Software Developer
 > > ZapMedia
 > >
 > > Phone: 678-420-2722                FAX: 678-420-5839
 > > email: michael.hirsch at zapmedia.com Web: http://www.zapmedia.com
 > > --
 > > To unsubscribe: mail majordomo at ale.org with "unsubscribe ale" in
message body.
 > >



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