Some workstations getting wrong subnet mask

[Spad]

We have a Windows NT network, and just added a win2k server. We loaded dhcp on this server, and it seemed to be working fine, until we discovered about 1/2 of the workstations are getting the incorrect subnet mask. This is preventing them from getting to some IIS server apps.

DHCP is configured as follows: Our scope is 128.127.0.1 to 128.127.255.254. Our subnet mask is 255.255.0.0. The lease duration is 8 days.

Some workstations (windows 98) log in fine, and get the correct subnet mask. Others (also win98) are getting 255.0.0.0 as the subnet mask. If they go into winipcfg and release all and renew all, it comes up with the correct subnet mask. But if they were to reboot, it would come up wrong.

I checked the subnet mask on all of our servers -- its all 255.255.0.0. Where is this 255.0.0.0 coming from? And how do I get rid of it?

 

[Designware]

Spad,

Did you ever resolve this issue? If so, please post it here since I am experiencing the same problem with Windows 2000 Server.

Thanks.

Designware

 

[itherd]

Can somebody help me on this. I am getting the same problem with my some of my win98 clients. If I release and renew manually it comes correctly. Server and clients both have recent updates.

 

[quake11]

Did the machines ever have static ip settings. Recheck dhcp scope and ip setting of the dhcp server in the manager tool. Recreate dhcp server from scratch. Watch your scope info as you set it up.

 

[itherd]

Thanks for the response. They are working fine with static IPs. And except these win98 pcs all others are working perfect with dhcp. Even these PCs also work fine sometimes. As I said I release and renew the IP to get the correct subnet. I did the recreation of scope also but in vein.

 

[quake11]

Not scope. DHCP server. Remove DHCP from server and recreate scope. Keep an eye on your event log for clues from errors or warnings.

 

[Jpoandl]

It almost sounds like your have a rogue DHCP server handing out bad addresses. Sometimes DHCP can come from Network devices such as Firewall/routers. To test, shut down DHCP server and see if you can renew your IP address. If so, you have a problem.

Also, check the TCP/IP properties on a problematic machine. You should be able to see where the DHCP address came from:

Connection-specific DNS Suffix . : company.com.
Description . . . . . . . . . . . : 3Com 3C920 Integrated Fast Eth
er (3C905C-TX Compatible) #3
Physical Address. . . . . . . . . : 00-0B-DB-24-xx-xx
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 10.10.1.34
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 10.10.1.1
****DHCP SERVER . . . . . . . . . . . : 10.10.1.10
DNS Servers . . . . . . . . . . . : 10.10.1.2
Primary WINS Server . . . . . . . : 10.10.1.2
Secondary WINS Server . . . . . . : 10.10.1.10
Lease Obtained. . . . . . . . . . : Wednesday, September 08, 2004
Lease Expires . . . . . . . . . . : Wednesday, September 08, 2004

-later

Joseph L. Poandl
MCSE 2003

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