connect: Network is unreachable
I recently re-installed the operating system on my Dell Server, running RH Enterprise AS 3.0. Somehow, I lost connection to my local network (and thus the Internet). I tested eth0 from the system diagnostic CD and it is perfect. The ethernet wire from the upstairs office seems to be working fine (the LEDs on the Dell eth0 connection flash when I try to ping the Dell). But when I try to communicate from the Dell, I get the message "connect: Network is unreachable".
The Dell has a fixed IP address of 192.168.123.75. I can ping this address successfully at the Dell and I can also ping the loopback address 127.0.0.1. But, if I try to ping anything else, I get the message: "connect: Network is unreachable". And, of course, I can't ping the Dell from any other computer on the network. I successfully added 192.168.123.0 using the route command and stopped and restarted the network using "ifdown eth0 " and "ifup eth0". But, then the routing table changes are automatically reset.
I tried everything useful that I could find in previous LinuxQuestions postings of a similar nature, but nothing helped.