Hi there:

I've installed CentOS on an old PC in order to learn how to use the closest OS to RHEL. The point is I'm sshing that machine over wifi from my Mac, and randomly, the connection disappears. One could think it's a wifi problem, but here's the funny thing: when the connection goes down, I ping the server and I get no response, but if I go the server and I ping back the Mac, the laptop starts ponging, and so does the server, immediately . Once both are ping-ponging, I can ssh again to the server and keep working for a while. After a random amount of time, I've got the same problem.

-Does anyone have any clue what could be happening?
-Is there any security feature on CentOS I should be aware of that could be provoking this behavior?
-Or do you think I could be having some issues with the AP? (by the way it's an AirPort Extreme)

Thanks for your time, guys!

Do you have the same problem when using wired connections? That should give you a starting point for troubleshooting, eliminating as many variables as possible.

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Not yet :P I'm still figuring out how to configure the eth0 device so I can connect directly both machines without a router between them. It should work since the Mac acts as a DHCP, but I can't make the CentOS server to get an IP address, nor make it work assigning a manual address. Later I'll try with an old router between them and I'll test it. Thanks for your help, mate!

Depending on how "clever" your NICs are you'll probably need a CROSSOVER network cable rather than a normal patch cable if you wish to wire them together directly.

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Not saying you're wrong, because that definitely used to be a problem in the past, but I haven't run across a machine made in the last 5 years that required this. I do direct connections like this all the time between many different machines, you just need one of them to be able to switch the pins, which any modern NIC can.

I would ignore DHCP, and just set both machines up with a static IP on the same subnet.

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I mentioned it as the OP states: "I've installed CentOS on an old PC", so there's no indication of the age of the machine.

I didn't catch that in his post, you're right that could be a problem then.

Actually, the machine is 10 years old. I know the laptop NIC can do that, and that's probably the problem at hand. I really hoped that having just one of the machines able to cross the wire would be enough. I guess I'm wrong Later I'll try with the router or maybe it would be better to get a crossed over cable since I could take advantage of both NICs being gigabit. Thanks, guys!

j

OK, so following the suggestion from suicidaleggroll, I've ditched DHCP and configured both NICs manually, and it worked, with no cable change. I guess I'm too used to the "just works" way of doing things on Mac So, one problem solved. Before configuring them manually, I've tried a last time, and checking the messages log, I've seen CentOS is actually trying to negotiate with the DHCP on the Mac side, but, for some reason it can't get the IP. I'll try in a couple of days with another DHCP and I'll see how does it works, then I'll investigate what's going on on that side.

On the ssh problem: on the last half hour it has remained connected. I'll be checking it for some time and I'll get you back on that, either is working fine, or not. Either way, I'll appreciate some tips on where to look at. I'm starting to like having troubles on my little test lab. For every little problem I solve, I learn at least to new things. Thanks for your time, fellas!

je

PS: Sorry if you find some grammatical error. Not a native speaker. Gracias!

TCPKeepAlive? I've just read man sshd_config, I'm no expert in SSH.

Hi, there:

I've been a couple of days moving disks around, and I putted aside the ssh problem. Then I came back this morning to it, and guess what?: I've spent all morning trying to fix a problem with the eth0 device when it was a problem with a faulty cable. Why I always forget to check the cable first...?

So I've read the manual for sshd_config and I've checked the file itself. The argument TCPKeepAlive was commented but I've set it to "no", just in case. Now ssh, looks stable. Thanks for the help, guys. Now, to the next step: setting up a nfs share and move files to it.

j;e