szhosain, got a question for you

[PoorManQ45]

Do you know what would cause a hardwired NIC to register as a Class B network with subnet 255.255.0.0 ?

I'll run into this problem every so often with some of the Dell Optiplex systems. I often have to resort to an OS reinstall to correct the issue.

Manually setting the IP configuration settings to an acceptable address causes a limited or no connectivity state.

I've had this occur in both XP and Vista!

I've figured out the Vista one. It's that it uses a DHCP Flag mixed with IPv6 that isn't compatible with certain modems/routers. You have to remove all registry entries pointing to IPv6 to correct this issue.

But I haven't been able to figure it out with Windows XP.

Is there a way to reset the Subnet alone to 255.255.255.0 and still leave everything else in automatic mode?

I think that when it mis-registers it's an authentication issue, correct?

Note, these are all connecting to home routers, so there arnt any B class networks in use.

Thanks for the help

-Brien

[szh]

I will hazard guesses here, since I do not know the answer really.

Do you know what would cause a hardwired NIC to register as a Class B network with subnet 255.255.0.0 ?

A swag: The home network probably has a DHCP server providing an IP address and subnet info (the server is the router or other Internet access box - like a cable modem, etc.). This DHCP server may be misconfigured and sends an incorrect netmask/subnet setting.

What is the IP address that the box gets from the DHCP server? If the IP address being used is in the Class B range, then the netmask may be defaulting to a Class B range if it is not configured.

If the router assumes that the netmask is 255.255.0.0, then setting it to other values will cause the connectivity to not work, of course.

I'll run into this problem every so often with some of the Dell Optiplex systems. I often have to resort to an OS reinstall to correct the issue.

Hmmm ... that seems like overkill. Have you tried using a DOS command window to simply do an "ipconfig/release" followed by an "ipconfig/renew" and seeing what the DHCP server provides then?

Manually setting the IP configuration settings to an acceptable address causes a limited or no connectivity state.

That makes sense ... the router may be expecting a Class B netmask.

I've figured out the Vista one. It's that it uses a DHCP Flag mixed with IPv6 that isn't compatible with certain modems/routers. You have to remove all registry entries pointing to IPv6 to correct this issue.

Interesting ... I have not had to do that! The twp Vista systems I have access to (one is a Dell ... Dimension though - not Optiplex) have no problems on the two networks that I use them on. My home DSL router is configured with the proper netmask, so the DHCP info it provides is correct.

But I haven't been able to figure it out with Windows XP.

Is there a way to reset the Subnet alone to 255.255.255.0 and still leave everything else in automatic mode?

Not that I know of. If you use DHCP, the computer assumes that all the info will come from the DHCP server.

Note, these are all connecting to home routers, so there arnt any B class networks in use.

Okay. But what is the actual IP address in use from the DHCP server? Is it a Class B address perhaps?

Sorry I can't be more informative ... this is an unusual situation. I hope some of the network experts chime in here. I will also ask our internal network expert here at work ...

Z

[PoorManQ45]

What is the IP address that the box gets from the DHCP server? If the IP address being used is in the Class B range, then the netmask may be defaulting to a Class B range if it is not configured.

Z

When you say box I assume you mean the computer:

It's showing a 169.x.x.x which I looked up and this is the address xp systems acquire when improperly configured, or not connected at all

The router's external IP address is like 67.x.x.x or 69.x.x.x which is correct for the service provider.

The routers internal address is usually 192.168.x.x

Hmmm ... that seems like overkill. Have you tried using a DOS command window to simply do an "ipconfig/release" followed by an "ipconfig/renew" and seeing what the DHCP server provides then?

Z

Tried that. I basically rebuilt the entire IP Stack and WinSock

And yes, an OSRI is kind of overkill, but I've spent hours on these issues and at a certain point you have to cut your losses.

Interesting ... I have not had to do that! The twp Vista systems I have access to (one is a Dell ... Dimension though - not Optiplex) have no problems on the two networks that I use them on. My home DSL router is configured with the proper netmask, so the DHCP info it provides is correct.

Z

Yeah, the Vista issue is a rare monster. And it is really a monster. You have to either rip out IPv6 completely or replace the router/modem with a different model.

It only occurs with Vista and X server.

Okay. But what is the actual IP address in use from the DHCP server? Is it a Class B address perhaps?

Z

The computer is pulling a 169.x.x.x number. Which is basically meaning it's not communicating.

Sorry I can't be more informative ... this is an unusual situation. I hope some of the network experts chime in here. I will also ask our internal network expert here at work ...

Z

Not at all. Thank you for taking time out of your busy schedule to try and help me.

Thanks

-Brien

[szh]

Our network experts responded. Pretty much what you said too.

Quote »On windows machines, when a system setup for DHCP boots up, it sends a dhcp request broadcast, if there is no reply from a dhcp server, it times out. The machine then automaticaly assigns itself an IP address of 169.254.250.x with a subnet of 255.255.0.0. If this happens on multiple systems, it would leave me to believe there is an issue on the DHCP server or the underlining network (maybe dropped packets due to a bad switch/hub/cables).

There is no way that I know of to configure a machine with a specific subnet mask while leaving the rest of the settings setup for DHCP. I hope this helps.[/quote]I guess you may need to explore whether the Optiflex systems that you are seeing this on, may have an Ethernet NIC that is (a) bad or (b) prone to having problems with so-so (but not dead) network connections.

Or, see if there is some time-out setting in the Windows XP DHCP client (when it tries to go get an address and other info) that can be extended out more ... so that it does not time out too quickly.

Do you have access to a network sniffer to check these out? Or are they all at customer sites that you cannot really get to? You might try to get the users to unplug and replug the cables into the computer and/or the other end (router/switch/hub), or try another cable, and see if that cures things.

Z

[PoorManQ45]

I guess you may need to explore whether the Optiflex systems that you are seeing this on, may have an Ethernet NIC that is (a) bad or (b) prone to having problems with so-so (but not dead) network connections.

Z

That's a good possibility. The new 755s have been having intermitent NIC issues. But it was an on/off situation. They don't use very expensive chips in them. Usually the lowest gigibit the broadcom offers.

So that's a possibility

Or, see if there is some time-out setting in the Windows XP DHCP client (when it tries to go get an address and other info) that can be extended out more ... so that it does not time out too quickly.

Z

I'll look into that one. Then possibly write a reg edit script and post it on a storage site. If the customer has another system that can get online i'd have them grab the script and run it. That'd automatically change the delays

Do you have access to a network sniffer to check these out? Or are they all at customer sites that you cannot really get to? You might try to get the users to unplug and replug the cables into the computer and/or the other end (router/switch/hub), or try another cable, and see if that cures things.

Z

They are all customer computers.

I do have them swap all known goods.

I guess I didn't mention this, but almost everytime there is atleast one other system plugged into the router that works just fine. So the router is configured properly, I think.

Our network experts responded. Pretty much what you said too.

Z

Wow, that's cool that you're able to get outside help like that. Thanks alot.

I'll look into the DHCP delay timeouts.

Note: the systems are almost always running XP Pro, never Home