DHCP Scope options for Security Devices

Jaime Campos
Jaime Campos used Ask the Experts™
Hello - I have a Security Device Scope set on my DHCP server. /20

What I want to do is assign another scope within my Security Device Scope for 10 Camera, 10 Card Readers and 2 Media Servers. How would I break that scope up into other scopes for the following devices, however using the Security Device Scope?


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Network Administrator
Hi, are they the first and last IP addresses in your DHCP scope and subnet mask /20?

10 Cameras, 10 Card Readers and 2 Media Servers => Total is 22 devices => Need 5 bits for host portion, so that 2^5 -2  = 30 can cover 22 => there are 27 bits for network portion.

So you need to break your network with subnet mask /20 to smaller subnets which include the subnet /27

For example:
Your network:

Security Device Scope1: 1000 devices => subnet /22 since you need 10 bits (2^10 - 2 = 1022) to cover 1000 IP addresses

Security Device Scope2: 22 devices  => subnet /27

=> Subnet for Scope1: Valid IP addresses from to

=> Subnet for Scope2: Valid IP addresses from to  

Hope this help!


It looks like Spac3_Pirat3 has a solution - please confirm if so or not.

Since I am here, just for the avoidance of confusion, the actual subnet is, I would guess: / 20

which contains:      through inclusive

I suppose you can write: / 20, but that still contains the same IPs as above, including through (inclusive) due to the way the bitmask works out.


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