DHCP Server Excludes Address Clusters Within a Valid Scope

SYMPTOMS

When a scope is defined so that it includes a valid set of addresses in a range, but it excludes or reserves addresses within the last 32 specific addresses of that scope, address clusters within the legal range of the scope may not be available to the dynamic host configuration protocol (DHCP) server for assignment.

For example, a scope with the following settings

   Range Start: 161.240.8.1
   Range End: 161.240.15.254
   Subnet Mask: 255.255.248.0

   Excluded Addresses:

      161.240.15.126 -- 161.240.15.150
      161.240.15.181 -- 161.240.15.184
      161.240.15.187 -- 161.240.15.254

   Reserved Addresses:

      161.240.15.185, 186
				

results in the following pattern of DHCP server IP address assignments:

   161.240.9.0
   161.240.9.224 -- 161.240.9.255

   161.240.10.0
   161.240.10.224 -- 161.240.10.255

   161.240.11.0
   161.240.11.224 -- 161.240.11.255

   161.240.12.0
   161.240.12.224 -- 161.240.12.255
				

In this example, addresses within the range of 161.240.XX.0 to 161.240.XX.224 cannot be assigned by the DHCP server even though they are valid addresses within the defined scope.