Routing Problem

[Alan McKinnon]

On Tuesday, 28 February 2006 20:39, Filipe Bonjour wrote:
> Hi,
>
> I can imagine two easy caises:
>
> 1) Missing default gw
>
> Is the Suse box marked as the default gateway? Run the command
> route, and if you don't see an entry called default, try creating
> it. I believe the command is
>
> route add default gw <name or IP of Suse host>

Best format is to use the SuSE box's IP - it's so easy to make a small 
mistake with network configurations and leave the workstations unable 
to resolve the name of the gateway...

> 2) Missing forward
>
> Is the Suse box forwarding packets? If not, it won't pass packets
> from one NIC to the other. Run the command:

That's not strictly true, and I only mention it because it can really 
mess up fault finding diagnosis.

If the Ubuntu box is properly set up with the SuSE machine as a 
gateway, he will always be able to ping the external NIC from the 
Ubuntu machine, even if IP forwarding is disabled. Sounds weird, but 
the reason is that those pings are not *leaving* the SuSE box so the 
kernel does not check the forwarding setting. Under those 
circumstances, he will not be able to ping his ISP (or any other 
machine connected to the external NIC for that matter).

> user at host $ cat /proc/sys/net/ipv4/ip_forward
> 1
>
> If you get "0", you should add the command
>
> echo "1" > /proc/sys/net/ipv4/ip_forward
>
> in a file read at boot. I don't know Suse, so I can't tell you what
> file to use.

It's in /etc/sysconfig somewhere, but it's SuSE, so it's best done 
from the Network page of Yast (there's a "router?" checkbox for this) 
otherwise the change is liable to be overwritten the next time Yast 
is run

-- 
Alan McKinnon
alan at linuxholdings dot co dot za
+27 82, double three seven, one nine three five