Re: What's better a few big subnets or several smaller subnets?
- From: "Scott Perry" <scott.perry@somecompany>
- Date: Wed, 20 Aug 2008 09:56:58 -0400
IP address subnetting can get people stuck in a class based mentality. IP
address subnets end up getting assigned based on the original Class B and
Class C subnets with subnet masks of either 255.255.0.0 or 255.255.255.0.
This results in IP address subnets of either 256 addresses or 65536
addresses without much sizing in between.
For example:
If you have 3 floors of a building, the IP address subnets get divided like
this:
10.0.1.0 / 255.255.255.0 - floor 1 LAN for PCs
10.0.2.0 / 255.255.255.0 - floor 2 LAN for PCs
10.0.3.0 / 255.255.255.0 - floor 3 LAN for PCs
and then continuing with...
10.1.1.0 / 255.255.255.0 - floor 1 seperate subnet for servers
10.1.2.0 / 255.255.255.0 - floor 2 seperate subnet for servers
10.1.3.0 / 255.255.255.0 - floor 3 seperate subnet for servers
and then so on for printers, management devices, etc...
Perhaps these 10.0.X.X subnets are used for the common LAN communication,
and subnets starting with 10.1.X.X and 10.2.X.X following the same 1,2,3,4,5
numbering in the third octet follow for printer, server, and other subnets
on each floor.
I like breaking things down into the available sizes in between of 512,
1024, 2048, 4096, 8192, 16384, and 32768.
How about this example where all addresses begin with 10.0.x.x:
10.0.0.0 / 255.255.255.128 - floor 1 LAN for PCs, up to 125
10.0.1.128 / 255.255.255.192 - floor 1 for extra systems, up to 61
10.0.1.192 / 255.255.255.224 - floor 1 for non PCs like time clocks,
kiosks, etc.., up to 29
10.0.1.224 / 255.255.255.240 - floor 1 servers, up to 13
10.0.1.240 / 255.255.255.240 - floor 1 for router loopback and switches,
up to 13
Summarized route for entire floor: 10.0.0.0 / 255.255.254.0
then repeat for each continuing floor:
10.0.2.0 / 255.255.255.128 - floor 2 LAN for PCs, up to 125
10.0.3.128 / 255.255.255.192 - floor 2 for extra systems, up to 61
10.0.3.192 / 255.255.255.224 - floor 2 for non PCs like time clocks,
kiosks, etc.., up to 29
10.0.3.224 / 255.255.255.240 - floor 2 servers, up to 13
10.0.3.240 / 255.255.255.240 - floor 2 for router loopback and switches,
up to 13
Summarized route for entire floor: 10.0.2.0 / 255.255.254.0
It is not as pretty on the eyes, but allows summarized routing and efficient
use of the address space. With only a few floors, memorziation of the IP
address prefix for a floor comes rather quickly and is only the concern of
the network administrator. I just hate seeing a block of 65536 IP addresses
used for a segment with only 100 PCs and a block of 255 IP addresses used
for a segment with only 10 hosts, and situtaitons like that. It probably
comes from formerly working in a company that owned a Class A address range
on the Internet.
-----
Scott Perry
Indianapolis, IN
-----
"Merv" <merv.hrabi@xxxxxxxxxx> wrote in message
news:3fe79809-1871-4916-9e72-7c3ffb4b4125@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I would use network 10 addressing as it would allow you to put some
meaning into the 2nd and 3rd octet should you wish to do that or just
assign randomly or sequentially. I would definitely not use
192.168.x.x addressing
10.floor_X.area1.device1
I would always go for smaller subnets for a whole host of reasons /
24 /25 or /26
.
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