Using a network and its limitations, ping timeout problems

Posted on 2005-03-09
Medium Priority
Last Modified: 2008-01-09
Is there a limit to the number of nodes on a private network?

All our PC's/Servers/Routers use a network.
Should we be using a network instead?
We have recently added more nodes and are beginning to experience sparratic ping issues (nodes timing out for 10 seconds or so, then returning requests when using ping 10.0.0.x -t). Where 'x' is the Workstation, router, or Server.

Gateway is..

Server A is.. (IP Address) (Subnet) (Gateway)

Workstation A (IP Address) (Subnet) (Gateway)

Ping the Server A from Workstaion A (ping -t)
Ping Workstation A from Server A (ping -t)

All requests are returned as expected, however after about 2 mins, or 5, or 3 mins eventually the request will timeout for 3-10 sec. then resume.  We have replaced  all our switches and have run a cable tester on all our runs, so the cabling is fine.  Any input would be apprecated.  I can expand on configuration and equiptment if requested.

Question by:jeffman5150
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Accepted Solution

richard_robinson earned 1500 total points
ID: 13503922
HI Jeff,

Yes there is a limit, but on a network I doubt you would reach it.

The network is what is called an A class network for private use, and would normally be used with a subnet.
It would really be the subnet which determines the size of your network though.

With a subnet you would be able to have 254 hosts. -, with being known as the network address, and being known as the broadcast address.

So, as long as all your hosts have a unique IP, and your network mask is correct for the number of hosts(machines) you have you should be OK.

I would check the machines you are pinging to see if they are being over worked, and check your network for other traffic from all of your hosts, as viruses/ network hardware failure can fllod a network effectively causing a DOS.

Hope this helps


Expert Comment

ID: 13505720
Could be a station is generating a large number of broadcast periodically.

A good next step would be to get a tool like ethereal and capture traffic.  Leave it running and stop it immediately after the pings are timing out.  I'd install it on both the sending and receiving stations so that you can see where the issue is occurring.

You should be able to see if the packets are arriving at the end station or not and you should be able to see what else might be happening on the network at that moment.
LVL 40

Expert Comment

ID: 13505801
As long as every node is directly connected to a switch, and you are not using repeaters or hubs, you are isolating your collision domains, but this does nothing to prevent broadcasts from interrupting traffic, as noted above...  And as also noted, the subnet mask determines the # of clients (nodes), that being 254 according to your current scheme...  I would look for possibly a jabbering NIC on the network and try replacing it..  Depending on the size of your network, you can try unplugging each node from the switch and try to isolate it that way..  (Ethereal is a cool utility, but be prepared to analyze a lot of packets..)

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LVL 18

Expert Comment

ID: 13508204
You can stay on 10.x.x.x network, that's not the problem. Try first to configure fastport on switches.

Author Comment

ID: 13508962
OK More Info....

It seems that all the ping issues are related to one Server. The PDC.  It is a Windows Server 2000, Prmary Domain Controller, Catalog Sever, License Server, Terminal Server License Server, and DNS.  Basically when this system stops responding all kinds of services related to that box also fail or hiccup.  All my workstations (approx. 60), and Servers (approx. 6) use it as the Primary DNS Sevrer.  Is it possible that I'm DOS'ing my own Server because there is a problem with my DNS, or too much traffic?  Should I be using my ISP's DNS as the Primary, and my internal DNS as the Secondary?
Right now the timeout issues orccur for 2-3 sec every 5 min or so. But its early in the AM and people are working.  I suspect that at lunch time all the users will be on the web and the timeouts will increase.
Also I can ping this PDC from multiple stations at the same time, and when it times out, it times out on everyone.  Interesting though is that if this PDC is pinging an external or internal address. It will not timeout in sequence with the internal stations when they timeout on the PDC.

Also I have done extensive traffic tests across our Servers and switches.  Normal traffic like coping (1GB) of data frm Server to Server or Workstaions to Server dont seem to affect the PDC ping issue.

I know this is a lot of info and ?'s Thanks for everyones help and responses.

Expert Comment

ID: 13509463
Were you able to watch traffic on the server during the outages?  Maybe using PerfMon or NetMon if you don't want to install ethereal.

I'd look at the NIC and IP stack on the PDC and make sure I had the latest drivers.

Could this be an ARP timeout issue?  Losing connectivity to multiple devices while maintaining a large file transfer seems like it could be the ARP cache on the PDC or the switch is timing out and it has to re-learn the MAC address of devices.

What kind of switch do you have?  is it manageable?  If so, check the stats on the link to the PDC for errors and also check the ARP timeout.  See if the problem frequency changes if the ARP timeout is changed.
LVL 40

Expert Comment

ID: 13511428
If it is the DC, then definitely look at the NIC..  and no, you need to keep the primary DNS server in-house and use forwarders for external DNS resolution..  If you don't you will be asking for real trouble in your network..

Is there anything else happening that might cause this to happen?  Power surges creating EMI interference (longshot)?  I just really hate these intermittent problems!

LVL 18

Expert Comment

ID: 13516490
If you have another DC you can install a secondary DNS, but I don't think this is the problem.

Configure Performance logs and alert to watch network traffic. You may also trace the processor utilization.

Author Comment

ID: 13566286

Fianlly just replaced the PDC with a new box.  Not to sure what was going on with the old one, but the new one seems to be working a lot better.  Thanks for everyones help.  It kinda blows that I never really figured out what the problem was, but sometimes its cheaper and quicker to replace the machine, than to keep troubleshooting.

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