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DHCP, scope problem

neal
neal asked
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Last Modified: 2013-12-23
I have set up a DHCP server with the range of 192.168.1.50 to 192.168.1.254 on a class C, also I have excluded 192.168.1.200 to 192.168.1.215.  The server has been assigning IP numbers just fine until it reached 80 and then it skipped to 178.  It is now up to 246 and i'm not sure what will happen when it hits 254.  Can someone tell me if this is a problem and what I might do to fix it?
 Thanks,
    neal
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Commented:
What Services pack / NT Version are you running ?

Author

Commented:
It's NT 4.0 and I have not installed any service packs yet...
I had SP1 installed but had to switch servers and never have reinstalled, I was also leary of SP2 and havn't touched it either.

neal

Commented:
I'd recommend sp2 at least. It contains a lot of DHCP
fixes including dealing with bad addresses.

The question is , even when it jumps to 178 does the number of available addresses tally. (ie. the range less your exclusions)..?

It should start at the lowest possible address and give the first available address it can find. The jump you described seems odd, and may be fixed by one of the S'packs. If it gets to 254 , it will scan the whole range for an available address , not just the next few in the range.
Eric BDirector of Information Technology
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Commented:
Go into dhcp config and check available addresses left. That will tell you if the skip is random or if it skipped for a reason.

Commented:
What mask are you using?
Commented:
This is a Known Problem from Microsoft see bellow....

PRB: DHCP Skips Addresses If Exclusion Range Included in Scope

Last reviewed: April 4, 1997
Article ID: Q140989 The information in this article applies to:

•Microsoft Windows NT Server versions 3.5 and 3.51 •Microsoft Windows NT Server version 4.0







SYMPTOMS

When you use an exclusion range with DHCP, addresses offered to clients may not begin at the first address in the scope.





STATUS

This behavior is by design.





MORE INFORMATION

Leases offered to clients from a DHCP scope will be offered consecutively, starting with the first address in the IP address pool. But if an exclusion range is added to the scope, the first lease offered may not be the first address in the IP address pool.

For example, if a scope is created using a starting address of 165.224.113.11 and an ending address of 165.224.113.249, the first lease address offered to clients will be 165.224.113.11.

Alternatively, if an exclusion range of 165.224.113.100 to 165.224.113.120 is added to the scope, the first lease address offered will be 165.224.113.75. Leases will be offered consecutively through 165.224.113.249, skipping the excluded range. After 165.224.113.249, the next leases offered will be 165.224.113.11 through 165.224.113.74 consecutively.

This may also occur when multiple ranges of addresses are included in the DHCP scope.

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