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I'm currently deploying a new site with an IP address range of 172.22.101.0 - 172.22.160.0 and wondering is it best to go with the subnet mask of /16 or /24? Each subnet will have no more than 2 or 3 hosts connected to a maximum of 100 hosts at this site. Each subnet is also on its own vlan so for example subnet 172.22.101.0 is vlan 101. At another site I have deployed I'm using the IP range of 172.23.101.0 - 172.23.160.0 with a /24 subnet and it is ok on that network there is the about 150 hosts connected what is the implications of using a /24 compared to a /16 subnet mask.

Many thanks for your reply in advance.

  • Is there any reason you aren't considering a netmask of any other length? – YLearn Jul 22 '15 at 21:29
  • I was just thinking of sticking with the /24 as on each subnet there are not many hosts and each subnet is routed via a layer 3 device if the subnets need to talk to each other – Andrew Jul 22 '15 at 21:35
  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 12 '17 at 3:54
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A /16 would not work, unless you want to take the entire 172.22.0.0 range. It would be easiest to manage with a single /24, but I would also suggest additional /24s be created for stuff like phones, wireless, servers, etc:

172.22.101.0/24 VOICE
172.22.102.0/24 DATA
172.22.103.0/24 WIRELESS
...

If you are unfamiliar as to why one should separate voice and data traffic, take a look at a tool called VOMIT.

In the past, Cisco didn't recommend any more than 200 hosts per subnet-- I'm not sure if this has changed (I'm not a CCDA/CCDE). With that being said /23 and /22s are used in production environments all the time with little to no consequence. Modern computers handle broadcast traffic much more efficiently than the old stuff.

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