Can I unplug LAN cable anytime?

Azazwa · 03-31-2009, 04:38 AM

Hi!

I need to unplug a CAT 5 from one computer and put in a different cable. (I just want to test the cables) Can I just unplug it while the computer is running?

The other side of the cable is connected to a switch.

Thanks!

linuxlover.chaitanya · 03-31-2009, 04:50 AM

There should be no problems with it. I have done this before without any issues.

maxy7710 · 03-31-2009, 05:31 AM

Well i'll suggest if its a production server or people are accessing it for UAT purpose then it will break the active connections, the moment cable is unplugged.
if its a standalone machine & using network as per the need of the user than first stop the network service & then do the cable change activity

Azazwa · 03-31-2009, 05:50 AM

Okay, I guess I should be more specific... ;-)

I'm building a cluster, and had VMware on the head node, but since it has its own DHCP, it didn't work very well with the DHCP server already on the head node's private interface.I uninstalled VMware but am getting this error when I try to image the nodes:
PXE-E32 : TFTP open timeout

I have looked at this:

Code:

root@gnlserv01 etc]# chkconfig --list tftp
tftp            on
[root@gnlserv01 etc]# /etc/init.d/xinetd restart
Stopping xinetd:                                           [  OK  ]
Starting xinetd:                                           [  OK  ]
[root@gnlserv01 etc]# netstat -an | fgrep -w 69
udp       0      0 0.0.0.0:69                  0.0.0.0:*

I have been thinking that perhaps the cable is faulty. That's why I want to unplug it, and use a different cable. The node gets its IP adress, but exits the Intel boot agent.

I would think that I could unplug the cable, but it you think there is grave danger, then please tell me so. Also, if you have any advice on the PXE error, it would be greatly appreciated!

maxy7710 · 03-31-2009, 06:14 AM

As u said that u r building a cluster, so in cluster have u made a service for IP including for SAN luns for failover.

cos normally in cluster u will have virtual IP & u make a service for it and u set a priority of the service for respective nodes.

heartbeat of the cluster is checked via Ethernet.

so if u r setup is fully functional & people are working on it then it will be a bad idea to unplug the cable.

Azazwa · 03-31-2009, 06:37 AM

Hi!

No, there aren't any other users on this cluster yet.

Code:

As u said that u r building a cluster, so in cluster have u made a service for IP including for SAN luns for failover.

cos normally in cluster u will have virtual IP & u make a service for it and u set a priority of the service for respective nodes.

SAN luns? What's that?

I also haven't set any priority for of the service for the respective nodes.

TFTP worked fine when I added the first node, (before VMware came into the picture) and now it's not. Could it be a hardware problem?

By the way, where does your qoute come from?

Thanks for your help!

maxy7710 · 03-31-2009, 06:54 AM

ok

i guess there's a communication gap

lets start again

* all u got to do is check the LAN cable, whether it is faulty or not with another one.
* Its a UAT system & no one apart from u are working on the server.

if the above 2 are correct then you can change the cable, as no one will be hampered from the activity.

Also can u explain in brief u r cluster setup

if u referred to my signature then its from movie " Rocky Balboa "

Azazwa · 03-31-2009, 07:49 AM

Hi!

Okay, I'm a postgrad chemistry student and rather clueless about computers. We want to do computational chemistry faster, so I have been given the task (as a project) to set up a cluster. I have used fedora 8 and OSCAR 5.1rc. I have a server node, and added one normal node. Everything went well, except that there were problems with finishing the OSCAR installation. (Torque and maui had to be helped manually)
But we have a small partition on the server node for XP, so I loaded VMware. Then people helped me to fix the torque and maui problems. I wanted to add the other nodes, but when I tried imaging them using OSCAR, I got errors in the network boot process. Probably due to VMWare also having a DHCP server. Since VMware isn't a priority at present, I uninstalled it. But now if I try to image the nodes, I get this PXE-E32 : TFTP open timeout problem.

I've checked the cables and switch with the cable and port of the first node that didn't have any problems.

I have rebooted the server node, checked that the firewall is disabled, and the things mentioned earlier in the post. I have no idea how tftp works or why it doesn't work anymore. I'm just about pulling my hair out of my head, because time is running out, and it seems to be such a stupid problem. I find it interesting learning new things in Linux, but my chemistry department expects me to do some chemistry calculations on the cluster as well and at present I'm just falling into one problem after the other.

That's why there aren't any users on this cluster yet. It's not close to being finished. Hope that explains a few things...

I would appreciate ANY advice.

:-)

Azazwa · 03-31-2009, 10:42 AM

Hi!

I found that one could unplug the LAN cable and nothing terrible happened, since no one else was working on the cluster. However, the cable was not the problem, not the switch, not the NIC.

Secondly, with Fedora 8, DO NOT USE the GUI to disable your firewall. Use #service iptables stop
Look at this site:
http://forums.fedoraforum.org/archiv...p/t-31587.html

Disabling the firewall properly, cleared the PXE-E32 : TFTP open timeout error.

:-)

Azazwa · 03-31-2009, 10:45 AM

Jippie!

maxy7710 · 03-31-2009, 11:28 PM

good to know that the problem solved