Re: Need help setting up route

[Michal Jaegermann <michal ellpspace math ualberta ca>]

On Fri, Apr 08, 2005 at 08:14:54PM -0700, Bob R. Taylor wrote:
> 
> The output of route -n shows:
> 
>  Kernel IP routing table
> Destination  Gateway     Genmask     Flags Metric Ref    Use Iface
> 192.168.0.0  0.0.0.0  255.255.255.0   U     0      0      0  eth0
> 169.254.0.0  0.0.0.0  255.255.0.0     U     0      0      0  eth0

That is a pretty good loking routing table.

> What I *think* this should be is:
> 
> Destination  Gateway       Genmask     Flags Metric   Ref   Use Iface
> 192.168.0.0  192.168.0.1  255.255.255.0   U     0      0     0  eth0

Nope.  If your gateway is 192.168.0.1 then this table should look
somewhat like this

Destination  Gateway     Genmask     Flags Metric Ref    Use Iface
192.168.0.0  0.0.0.0  255.255.255.0   U     0      0      0  eth0
169.254.0.0  0.0.0.0  255.255.0.0     U     0      0      0  eth0
0.0.0.0      192.168.0.1    0.0.0.0   UG    0      0      0  eth0

The same information printed by 'ip route' should be close to that

192.168.0.0/24 dev eth0  proto kernel  scope link  src 192.168.0.3 
169.254.0.0/16 dev eth0  scope link 
default via 192.168.0.1 dev eth0 

This should be established by scripts which are bringing your
network interfaces up _if_ you have 'GATEWAY=192.168.0.1'
either in /etc/sysconfig/network or in
/etc/sysconfig/network-scripts/ifcfg-eth0.

> How do I fix this?

One of ways is to run 'neat', fix your network configuration by filling
forms you will get and restart eth0.  Or you can go with an editor 
and edit configuration files directly although it helps if you
realize what you are doing.

> What file(s) do I need to edit?

You will find various system configuration files in /etc/sysconfig/.

Also in a configuration like in your drawing if you want 192.168.0.3
be able to talk to the outside world you need some kind of NAT on
192.168.0.1 and also IP forwarding turned on there (look at
/etc/sysctl.conf).

> I really need for
> these computers to talk to each other again!

With your current routing table 192.168.0.3 and 192.168.0.1 should not
have any trouble talking to each other.  If they do then there are some
other reasons for that (your network card is not "alive", you are
blocking communication on firewalls, your network cable is broken or
incorrectly wired, .... ).  You need a gateway only if you try to
connect to something outside 192.168.0.0/24 LAN.

You realize that if you have 192.168.0.3 and 192.168.0.1 connected
"back-to-back", like in your drawing, then you may need a "crossover"
network cable although there are some network cards which will adjust
themselves?  Or you are using a 10T cable?  To find that and cards with
such connectors would be quite hard nowadays.

   Michal