network problems with sco

UNIX SCO
1

SCO unix 5.0.5 - Suddently network lost & has to be reboot. I try to stop TCP & start TCP. but no connection. Any idea about that.

thanks

2

The best results I've had in diagnosing network problems related to the NIC have been through the diagnostics provided by the card manufacturer and running under DOS. Using the diagnostics on 3Com stuff that I've standardized on requires a floppy and a DOS boot diskette but it could all be put on a CD if you have CD boot capability.

3

Dear Edfair,

I changed the NIC. also the same problem. we are using 3com 3c90b cards which is automatically detected by Unix. we have another server which is doing the same thing. When you lost the network you have to restart the server.

thanks

4

I can't recall the reason but I stopped using the 905B at some point and only install the 905-TX version, which has given good service. Or an earlier PCI based one, can't remember the type, and when all else fails I fall back to the 509 and the ISA bus.

You might try running the DOS based diagnostics and see if anything shows up but based on the multiple failures on that card I suspect that you would be better off getting the TX version.

What kind of system are you dealing with, hardware wise? Most of mine is PII based but I may have some PIII.

5

i am using intel Xeon 3.00ghz 2 processor pc's. i may try with tx NIC cards

thanks

6

I would suggest that perhaps you are running out of tcp connections or you have a bad nic on your network.

If you check scoadmin / network / tcp of the NIC you should see how many tcp connections you are willing to allow. We set up most machines to be 512 but you can set it up any way you like.

I have seen several times, SCO 5.0.x boxes that the network seems to just die randomly and upon reboot then it works flawlessly. Usually it is one of two things, either there is a bad NIC on your network that is corrupting arp packet requests (wireshark or another packet sniffer should show you this symptom within a few minutes, and will usually be miss-labeled "Gratuitous Arp Requests" and should be called "non-conforming arp requests") or you are having something make more socket connections that you have tcp connections. As soon as you reach the number you specified, the NIC will stop processing all traffic.

7

We check the network by using wireshark. there are plenty ip's giving Gratuitous Arp Requests. Do you have any idea to block these from UNIX servers. without shutting down lot of devices on the network.

thanks

8

Hi everyone,

I have the exact same problem with two of my servers running on SCO 5.0.5.

The first one is part of a tiny network (about 6 or 7 'clients') so I don't think the number of TCP connections is the reason. Thanks to your previous posts, we are about to install a packet sniffer on the network.

The problem is that I'm not really a network expert (and my native language is french) so I'm a bit lost in all the information the sniffer will give to me. What am I supposed to search for ? Gratuitous ARP Requests ? I've read that those requests are sent to check for double IP, is it true ?

Thanks in advance

edit : I'm trying to install tcpdump on my server. When I try to launch it, I have en error message : "no cards available to use in /dev/mdi". And when I try to give him the interface I want, it says "Can't open device - Device busy". Do I need to install a second card on the server ?

9

we try to disable some devices after checking sniffer. but still we got same problem. after we put the server2 behind firewall. it solve our proglem. if you dont have firewall, may be you can adsl router to put in another segment since NATting is there. i didn't try this. remove devices one by one in your small netwrok & try also.

thanks