[Maintain] Help with creating a new subnet...

Dawn Keenan dkeenan at uwaterloo.ca
Mon Oct 1 17:44:17 UTC 2007

Nielson, Adam wrote:
> Ok, please pardon my complete ignorance and lack of understand; but I don't understand.
> I followed your documentation at http://nsbuild.uwaterloo.ca/doc/newsubnet.html and why are you using the IP range to, yet when you create the subnet its
> I have A.B.168.0 through A.B.171.255 completely for myself.  I put the IP range as this, but I cannot create a subnet.  I know my subnet mask is, but I cannot for the LIFE of me figure out what to put (after several failed attempts) in subnet.  I have even tried without VLANs, I have tried the range to be A.B.168.0 to A.B.168.255, and with/without VLANs, and still nothing.
> Again please pardon my ignorance and complete lack of common sense, I am just recently assigned to DHCP administration, and obviously have a lot to learn.

Since my documentation is primarily for our local administrators, it may 
contain localisms but does show what I've tested as a viable task order 
in the (initially confusing) setup of subnets.  I see where the screen 
shots are inconsistent and should add fixing it to the end of my list of 
things to do.

The order of operations that works for us at UW is:

  - ensure an IP range that covers part of the subnet exists and is 
enabled so it's not forgotten later (e.g. A.B.168.0 to A.B.171.255 if 
you want one range for the whole subnet, though we've found IP ranges 
wider than 500 to be unwieldy and a range covering an entire /16 to be 
downright unusable)

  - create a VLAN with a reasonable name and ID because the "Create 
Subnet" interface wants to associate a subnet with a VLAN (we don't use 
Maintain for VLAN management so this is a nuisance documentation step 
for us)

  - create the subnet with the aforementioned VLAN, using the base 
address and mask (e.g. A.B.168.0 and

  - assign a "network" host entry to the subnet (our local policy, 
requires an enabled range, a VLAN and a visible subnet)


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