Re: [linux-tr] communication outside subnet

["Gilbert Ramirez Jr." <gram@verdict.uthscsa.edu>]

As Carsten Brink said:
> 
> I hope someone can help me or explain what commands are actually carried
> out during the =93cure=94-process described. Knowing the commands might h=
> elp
> locating the solution.
> 
> Thank you in advance,
> 
> 		Carsten Brink
 
It sounds like some process (automated?) is removing your default gateway
from the routing table.

When IP is working fine, run this command:  netstat -rn

You'll see something like:

Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.44.0    0.0.0.0         255.255.255.0   U      2000 0          0 tr0
127.0.0.0       0.0.0.0         255.0.0.0       U      3584 0          0 lo
0.0.0.0         192.168.44.254  0.0.0.0         UG      576 0          0 tr0

Here, my tr0 card is 192.168.44.99, and is therefore on the 192.168.44.0
network. With the first entry, I shoul be able to being any IP address on
my local subnet.

The second entry is the loopback interface. We'll ignore it.

The 3rd entry is the default gateay, 192.168.44.254. This entry in my
routing table tells me how to get to IP hosts off of my local subnet.

When your routing fails, first ping your default gateway. Then run 'netstat
-rn' again.

If you can ping your gateway and your routing table doesn't have the
0.0.0.0 entry, then some program is messing up your routing table.

If you cannot ping your gateway, then your router is going up and down all
the time. I doubt that this is the case.

To fix your defaulte route manually,:

route add default gw 192.168.44.254 metric 1

(of course, 192.168.44.254 is *my* default gateway. Put in the IP address
of your gateway.)

--gilbert

-- 
Gilbert Ramirez                Voice:  +1 210 358 4032
Technical Services             Fax:    +1 210 358 1122
University Health System       San Antonio, Texas, USA