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DHCP Subnet Mask Problem

By jim ·
On my 150+ machine network, I have two or three that get the wrong subnet mask when they renew their IP addresses via DHCP. (DHCP server running NT 4.0). Instead of renewing 192.168.0.X with a subnet mask of 255.255.255.0, they get the right addressrange, but a 255.255.0.0 mask. Since it only affects a few machines, I suspect it is a client problem, not a server problem. Anyone ever seen this before? Thanks!

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DHCP Subnet Mask Problem

by hacbmis In reply to DHCP Subnet Mask Problem

The only thing I can see that would make the mask change would be the number of subnets or nodes DHCP is set to, ie.. 192.168.0.0 to 192.168.0.255.

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

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DHCP Subnet Mask Problem

by timwalsh In reply to DHCP Subnet Mask Problem

Is it the same 2 or 3 computers that have the wrong subnet mask?
Is it possible that these computers have more than 1 NIC? Maybe the second NIC has a fixed IP address with the wrong subnet mask defined.
Is it possible you have a rogue DHCP serversomewhere on your network?
Are you running a backup or secondary DHCP server someplace on the network?
Is it possible these particular computers actually have fixed IP address with the wrong subnet mask defined (although I imagine you've checked that)?

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

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DHCP Subnet Mask Problem

by EricRyd In reply to DHCP Subnet Mask Problem

Check your lease times, make sure that computers aren't getting new IP's and filling up the address pool.

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

All were good ideas... I replaced the two NICs involved and...so far... the problem hasn't recurred. Thanks to all!

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

I still think it is some kind of NIC problem... why would it only happen to these two machines? I can't believe it is a system problem or it would happen to some of the others. AAAAARRRRGGGGHHHH!

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DHCP Subnet Mask Problem

by apaul4 In reply to DHCP Subnet Mask Problem

Have you tried comparing results from ipconfig /all and an arp -a to see if there are any static or stuck addresses that show up?
Or when you do the IP config /all does the DHCP server IP listed match that of machines that get correct address configurations?

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

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DHCP Subnet Mask Problem

by jim In reply to DHCP Subnet Mask Problem

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