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Re: 2 IPs on 1 Network Card



Stephen Hargrove <stephen@exitwound.org> writes:

> This is a weird one, so hopefully someone out there has tread before me.
>
> eth0 is defined as 192.168.29.43.  On that same NIC, I need to define
> eth0:0 as 216.63.319.43.  Here's my /etc/network/interfaces:
>
> auto eth0
> iface eth0 inet static
        (192.168.29.43/24, gateway on .254)
>
> auto eth0:0
> iface eth0:0 inet static
> 	address	216.63.139.43
> 	netmask	255.255.255.248
> 	network 216.63.139.0
> 	broadcast 216.63.139.255
> 	gateway 216.63.139.134

First off, this set of settings isn't consistent.  If the netmask is
right (a /29 network), then that address would have a network address
of 216.63.139.40 and a broadcast address of 216.63.139.47; if you used
the same convention for the gateway machine, it'd be 216.63.139.46.
Alternatively, those settings are workable with a netmask of
255.255.255.0 (a /24 network).

> This sets up fine, but I can't communicate out eth0:0.  I'm positive
> that it has something to do with the default gateway.

Linux's default routing policy is:

-- Is the destination address on a local network?  Send to that
   interface.  Otherwise,
-- Send the packet to the (single) default gateway, which must be on a
   local network.

If you don't want to define a more complicated routing scheme, you
should set up /etc/network/interfaces so that one iface stanza but not
the other has a 'gateway' line.  '/sbin/route -n' will show you the
current routing table.

-- 
David Maze         dmaze@debian.org      http://people.debian.org/~dmaze/
"Theoretical politics is interesting.  Politicking should be illegal."
	-- Abra Mitchell



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