Not long ago we expanded the range of our network segments. This meant reconfiguring our DHCP server to assign IP addresses using the new ranges. While normally if you configure a 255.255.255.0 segment it isn’t possible to set the address range to x.x.x.0 to x.x.x.255. Those x.x.x.0 and x.x.x.255 addresses are normally used for broadcast messages and so they can’t be assigned.
Now when we wanted to set the ranges to 255.255.252.0 the address ranges got expanded from x.x.x.1 to x.x.x+3.254. However we couldn’t select x.x.x.0 or x.x.x+3.255 to be within the range, but we could select the range to be from x.x.x.1 to x.x.x+3.254. Since Windows DHCP server was smart enough to not include the broadcast addresses in the 255.255.255.0 mask I thought it wouldn’t assign the broadcast addresses in the 255.255.252.0 range either.
However when I looked at the DHCP leases it was assigning those addresses to computers. Addresses like x.x.x.255 or x.x.x+1.0 were assigned to computers making them not able to use the network as it should. So what I did was add every x.x.x+[1,2,3].0 and x.x.x+[0,1,2].255 within the range to the exclusion list and deleted the leases from the DHCP server. This way those broadcast addresses wouldn’t be assigned to workstations and the network connections would work perfectly again.
