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Wireless Networks Thread, IP addressing scheme feedback wanted in Technical; Originally Posted by rosswilson I think he is proposing to use the a /21 network mask for his subnets. It ...
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    Quote Originally Posted by rosswilson View Post
    I think he is proposing to use the a /21 network mask for his subnets. It just so happens that he has chosen to use the 10.x.x.x IP address format. So the quote above is not strictly true; yes 10.x.x.x subnets do exist and they commonly have a /8 subnet mask, but in this case the OP has chosen differently.

    A /21 subnet mask would allow up to 2046 devices on one subnet. However, I do agree with you that it remains good practice to keep to the 512 devices per subnet rule.

    Ross
    I understand he will be subnetting the 10.x.x.x network, but I would still stay away from using a Class A network unless there will actually be a need for it. Even with subnetting it is a waste of a Class A network because it will be extremely underutilized. Use a Class B network.

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    rosswilson's Avatar
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    Quote Originally Posted by cbrasga View Post
    I understand he will be subnetting the 10.x.x.x network, but I would still stay away from using a Class A network unless there will actually be a need for it. Even with subnetting it is a waste of a Class A network because it will be extremely underutilized. Use a Class B network.
    But if he is subnetting his network with a /21 subnet mask then the whole concept of Class A, Class B, and Class C networks disappear. What was once referred to as a "Class A" network is simply a subnet with a /8 subnet mask. The concept of Class ABC networks was before CIDR subnetting was introduced.

    Quote from Wikipedia:

    Classful addressing is obsolete and has not been used in the Internet since the implementation of Classless Inter-Domain Routing (CIDR) starting in 1993. For example, while 10.0.0.0/8 was a single class A network, it is common for organizations to divide it into smaller /16 or /24 networks.

    A classful network is a network architecture used in the Internet until around 1993. It divides the address space for Internet Protocol Version 4 into five address classes. Each class, coded in the first four bits of the address, defines a different network size (number of hosts), or a different network type (unicast or multicast).


    Maybe I am interpreting you wrong, but how will the OP be "extremely underutiliz[ing]" this "Class A" network?

    Ross

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    To put it into a simple physical analogy, lets say the network addressing space is a piece of land and a subnet is a house. You can build 10 houses on a 16,000,000 acre piece of land and even though each house is self-contained and cozy, it's a waste of land for just those 10 houses.

    I'm coming from the arena of having a logical and orderly network. Why use a class A if you're subnetting down to only a few networks or hosts?

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    There is a need for the 10.x.x.x subnet. Eventually all of the schools in our diocese will be connected by a WAN so there will be thousands of devices within the range. The range at my school will be 10.208.48.0/21, which is excessive, but the reasoning for giving such big scopes for particular devices is so that if I had to go to another school I know roughly what the possible ip of a device could be.

    PS you're welcome to come and help, but you would have to pay your own way sorry

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    Thanks for the good analogy I was trying to come up with one earlier too.

    But what real "waste" is there in using the 10.x.x.x IP range? After all, the whole 10.x.x.x IP range is private. By choosing to use 10.x.x.x instead of 192.168.x.x or 172.16.x.x just means actech has a lot more IP addresses to play with (3 octets) ... and it would seem he will need a fair few IPs if all his other schools are to be connected onto the same LAN/WAN/MAN.

    10.0.0.0 - 10.0.7.255 would be his first subnet, then 10.0.8.0 - 10.0.15.255 would be the second and so forth. 10.255.248.0 to 10.255.255.255 would be his last subnet.

    By using the 10.x.x.x private address range actech can have 8192 (/21) subnets. If he had used 192.168.x.x he only has two octects to play with, thus reducing the amount of (/21) subnets he can have to 32.

    Ross

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    I'm simply advocating, right sizing an organization's network (not subnets, the whole network). With a /21 on a 10.x.x.x network that accommodates 8192 networks with 2046 devices per network. So if the organization is going to come close to using 8,000 subnets (including room for growth) then go ahead and use a 10.x.x.x network. If an organization will have closer to 30 subnets, which is more realistic, then use a 172.16.x.x /21 allowing for 32 networks and 2046 hosts per.

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