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TCP/IP headache

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13 replies

by benci

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Hi!
I have installed a W2K server on my network which also is a domain controller (I upgraded my NT4 PDC into W2K). It is configured with a LAN IP. For some reason I cannot access the internet. Also the IP address cannot be pinged from any other PCon the LAN. Shares on this PC can be easily accessed via NetBIOS names. I have tried uninstall and reinstall TCP/IP, repair Windows etc. to no avail. I cannot ping any other LAN or WAN from this PC. If I ping the loopback it responds OK.
Any help would be appreciated.
Thanks

13 replies

by zman750

Get yourself a packet capture tool such as ethereal or netmon. Install it on your W2K PDC. Then ping from a different box. Look for these things:

-ICMP echo requests.
-arp requests/replies with your stations MAC

If you don't even see the arp broadcasts then you aren't on the network, but since you can get your shares you probably should see the arp.

If you do see the arp requests, make sure your server is responding with a correct arp reply msg.

If all that is correct, see if the ICMP echo request packets are making it to your server from your test box.

by benci

I notice that when I start the Server in safe mode with networking, it works fine , which means it connects to the internet and it can be pinged from within LAN. It seems to me like some other service is preventing TCP/IP from functioning properly. I kept records on the services that were running in Safe Mode and started in Normal. When logged I went and stopped all the services that were not started in Safe Mode. Still it didn't work. I do not know else to try.
Thanks

by madmark

Do you have a DNS service running? If you do, add a DNS entry into the IP properties of the workstation. If you don't create a host file on the workstation and add the server's name and IP address to it.

by evillage

Questions:

1. Describe basic physical network:
a. number of workstations
b. number of servers
c. how they are connected (hub, switch, etc)
d. router?
2. How does this network connect to the Internet?
3. What protocols are installed on the server?
4. What protocols are installed on the workstations?
5. What is the tcp/ip configuration of a typical workstation?
a. IP address
b. Subnet mask
c. Gateway
d. DNS
e. WINS
6. What is the tcp/ip configuration of the server's LAN connection?
a. IP address
b. Subnet mask
c. Gateway
d. DNS
e. WINS

by ghstinshll

The simplest idea to come up with here is that your subnet mask on the PDC may be wrong, making it so nothing can talk to it, yet the broadcasts will work.

You're missing some info, as mentioned above, butcan you ping it'self from that machine? Have you tried replacing the NIC? ALthough I'm not a friend of the "check cabling first" theory, it's possible as well...

by benci

Yes I can ping myself. The subnet mask is OK. I have tried different NIC but nothing changes.

by lordinfidel

Pinging yourself only says that the adapter is configured correctly. That is to say, the adapter is working.

It is not leaving your nic so it is really not a valid test.

The IP you need to ping is your gateway. Once you can ping your gatewaythen you are good to go.

Unless of course your gateway is having issues. But technically, once you can ping your gateway (which should be on the same subnet you are on), you should be able to ping any other host on the same subnet without a problem.

Again, look at your routing table. Make sure that you have the correct routes in there.

An incorrect route will mess up your day.

by lordinfidel

first off, netbios will have nothing to do with your problem. It has nothing to do with tcp/ip, so pretend it does not exist at this point. Nor will DNS, this is all at the IP level.

1st, is this a static IP? If so check the ip, subnet mask and gateway.

If it's not, then we need to check what address dhcp gave it.

Open up a command prompt. (start/run/type command, press enter)

type in ipconfig /all

look at the info, is it correct?

now try to ping your gateway,
ping gateway-ip

If you can not ping your gateway, look at your routing table (assuming that you have checked your cables/replaced the cables etc, verify the cables work via a lan tester)

type route print

you should see a routing table. Make sure that it is correct. If you do not know how to read a routing table, this is a perfect time for you to learn.

It is basically simple. From left to right it reads: to get to (a ip or network) with a netmask of use this IP to get there.

to get to theinternet you MUST have a route of
dest 0.0.0.0
mask 0.0.0.0
gateway (your networks gateway)

if your local network is 192.168.1.0/24 and your ip is 192.168.1.15 then in order to get anywhere on your local network you will have a routing entry that looks like:

192.168.1.0 255.255.255.0 192.168.1.15 1

As long as you have that stuff in there, you should be able to ping your gateway. If you can not, do you have ANY personal firewall stuff on there or on the gateway that would block ICMP messages.

Use tracert -d DestIP to see if it is even leaving your interface.

Make sure you do this all from the machine you are trying to diagnose and not from another machine.

by benci

I am using DHCP right now. The IP parameters are obtained correctly from DHCP server (ipconfig /all shows that). Still I can't ping anything (either gateway or any other LAN ip). I am not using any firewall that would stop ICMP packets. Also the routing table looks OK from the command line. Using tracert from command line shows that no packet leaves the box (it times out). Same results are obtained even when I assign a static IP.......
However here is something new. When I start Windows into safe mode with networking, everything works normal. No problem at all. Is it possible that some service is conflicting with TCP/IP !!!!!!!??????? I recorded the services that were running in Safe Mode With NEtworking. I restarted into normal mode and after I logged on I stopped all services that were not running in Safe Mode and made sure only services running in Safe Mode are running, but no luck. Is this the right way to investigate which service is screwing TCP/IP (if it is at all)????
Thaks for the attention

by lordinfidel

Open up TaskManager while in safe mode, go to processes, and take screen shots of all of the process that are running.

Safe mode does not load up anything from the registry. Which is why whatever is stopping your adapter from working is not doing so in safe mode.

then boot normally, go back to the taskmgr/processes and see what is running.

Also, how many adapters do you have?

Also check out your startup folder and see what is there.

Also if this is a w2k system, look at the IP Security policies. Something/Someone may have set up a security policy that denies all traffic.

In the properties of the adapter, look at tcp/ip properties/advanced/options. Make sure IP security is set to not use IPsec and nothing is set in tcp/ip filtering.

How many different protocols do you have set up for that adapter.

If you are strictly a windows 98 and higher shop, you should only need tcp/ip installed (besides client for ms netwks and file/print sharing)

Unless you are running netware you do not need ipx/spx. Don't need appletalk or even netbeui.

by supreme21

What kind network adapter are you using? I know for Intel adapters they have power down problems. If you are using a Intel adpater or IBM (they are the same) I think I know whats wrong.

by bootstrap

and it has been awhile - so I hesitate to venture in too far.

1) pinging the loopback address verifies tcp/ip configuration ONLY. You will get a successful result even with a bad nic.

2) try pinging the IP ADDRESS of the card in both safe mode and in normal mode. If you can ping the loopback but not the actual IP address - replace the card .... WITH A SUPPORTED NIC.

3) differentiate between a name resolution problem and an IP problem. USE IP ADDRESSES only for diagnostic work. Once you can ping with IP addresses, then move to fqdn's.

4) Try creating a dos networking disk and see if you can connect with 16-bit drivers. Always an interesting troubleshooting/diagnostic technique.

5) It smells like a hardware issue, but ... have you tried upgrading the NIC driver??

6) PLEASE swap out the NIC for another - preferably a different brand and a recent vintage. If the NIC swap doesn't work, then it gets ugly and you need to focus on IP itself and probably perform amanual uninstall/reinstall.

I have also left a ton of things out ... hope it helps.

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