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Natldiag

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Subnet question for private B class 172.16.x.x ip range

I support a network that is setup a lot like this example: ( https://www.experts-exchange.com/questions/21105296/IP-and-Subnet-Question.html?sfQueryTermInfo=1+172.16+255.240.0.0+privat )
172.16.1.x for routers
172.16.2.x for switches
172.16.3.x for servers
172.16.4.x for network printers
172.16.5.x for management devices
172.16.6.x for DHCP
172.16.7.x for wireless access points
etc., etc.
with a subnet of 255.255.0.0

After reading RFC 1918 ( http://www.faqs.org/rfcs/rfc1918.html ) that states that a private B class IP should have a network address of 172.16.x.x with a subnet of 255.240.0.0. I can switch my subnet right now from 255.255.0.0 to 255.240.0.0 without much difficulty. After reading the post on Experts Exchange I am a little confused on what is the best practice. Should I have the /12 subnet or is the /16 subnet for the private range known as an acceptable practice?
Avatar of A Edwards
A Edwards

If I am reading your info correctly
you want to know if you should be using a subnet mask of 255.240.0.0 ( answer is no )
You should use subnet mask 255.255.0.0 because you are using a Class B.

Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800a67f5.shtml
I hope this helps!

To seperate your networks you would use a subnet mask of ( 255.255.255.0 ).
With this mask it will break out your networks.
172.16.1.x for routers
172.16.2.x for switches
172.16.3.x for servers
172.16.4.x for network printers
172.16.5.x for management devices
172.16.6.x for DHCP
172.16.7.x for wireless access points
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ASKER

learn2earn thanks for your feedback. Currently we do not have it subnetted, so we just have one subnet with the /16 subnet. Looking at RFC 1918 ( http://www.faqs.org/rfcs/rfc1918.html ) , it looks like 172.16.x.x - 172.31.x.x is reserved for a private range? Could you please explain section 3 RFC 1918 to me if it is incorrect that you would use the 255.240.0.0 subnet for a private 172.16.x.x range? I know that normally the  last two octets are subnetted in a class B range, which is why I became curious about this.
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Les Moore
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