Currently I have 3 machines hooked up to a switch (Foundry EdgeIron 8X10G). Up until two days ago, two of my machines were running RHEL 4.0 and the third was running 5.0. I had them working together fine; I could ping and ssh the other two machines from any of the three. For testing purposes, however, I needed RHEL 5.0 on the two machines that didn't have it. I installed it, and all of a sudden none of the machines communicated with each other anymore. What could be wrong?

Possibly pertinent information:
-I had first disabled DHCP and statically set the IP address; that didn't work so then I enabled it, but there is no DHCP server, so that didn't work either. Currently they are statically set again.

-The machine whose OS I didn't upgrade has two lights on the back of its NIC: a flashing orange one and a green one (i.e. it is physically connected to the switch and it is active). The other two machines only have the flashing orange one (only physically connected). Also, for the two machines that only have the flashing orange one, the "Link/Act" LED on their port in the switch is off.

-My hostnames and IP addresses are:
4008a4=10.125.8.4
4003a6=10.125.3.6
4003a4=10.125.3.4
Netmask for all is 255.255.0.0
Broadcast for all is 10.125.255.255
4003a4 is the one that was not upgraded.

Thanks in advance for any help.

assuming that you've got openssh package installed, it might be that port 22 is closed

How do I check if I have openssh package installed? And how do I open port 22?

In the command line as root you try to type:
you'll see if it's installed or not

To easily control your firewall, you could either learn about iptables (google it) or install e.g. firestarter - a gui firewall administration tool (yum install firestarter)
hth

These machines are not connected to the Internet, so I can't use yum to install packages. However, I am currently looking at a (very very long) iptables tutorial, so I'll write back on this thread if I have figured out what to do/have finished reading the tutorial and still don't know what to do. Thanks very much.

issue:
rpm -q openssh
to see if it's installed at the moment (correct me if i'm wrong)

system-config-securitylevel

Update: OpenSSH is installed. I used system-config-securitylevel on 4003a6: disabled SELinux, added eth0 and eth1 to trusted devices, and allowed NFS4 service (SSH was already allowed). Haven't been able to test the network, as 4003a4 is being used by another team right now and 4008a4 has been having problems with its NIC. However, I don't think this worked, as the lights (Link/Act on the switch and the transmit light on the NIC) are not on.

With regards to 4008a4's NIC, I took it out, to write down any possibly relevant information on it (i.e. everything written on the card). I then put it back in, turned the computer back on, and found out that the OS was no longer recognizing eth0; what did I do wrong, and how do I fix it?

Update: I believe that it was actually the firewall that was disrupting my plans. Therefore, I reinstalled (yet again) and this time, chose to disable the firewall. Of course, because there are no other machines with active NIC's connected to the switch, I can't test if this is correct. Thoughts?

And if anyone has any ideas about the NIC on the other machine (4008a4, the one I mentioned in the previous post), please post your comments on this thread:
http://www.linuxquestions.org/questi...tartup-649894/

Thanks very much.

It works! All I had to do was install the driver for the card. The reason behind this is because I did a clean install, the drivers were deleted from the previous install. 10G Ethernet card drivers are not included in RHEL 5 (and most, if not all, other distros).

Thanks very much for all of your help! I really appreciate it. And I learned a lot in the process (that's the important part, right?). :-D