Enterasys Vertical Horizon VH-2402S2 Spécifications télécharger pdf (Page 149)

9033691-01 VH-2402-L3 Management Guide 141

11111111.11100000.00000000.00000000 255.224.0.0

Subnet Mask

00001010.00100000.00000000.00000000 10.32.0.0

Network Address

00001010.00101010.11111111.11111111 10.32.255.255

Broadcast Address

This example uses an 11-bit subnet mask. (There are 3

additional bits added to the default Class A subnet mask).

So the number of subnets is:

– 2 = 8 – 2 = 6

Subnets of all “0”s and all “1”s are not allowed, so 2 subnets

are subtracted from the total.

The number of bits used in the node part of the address is

24 – 3 = 21 bits, so the total number of nodes is:

– 2 = 2,097,152 – 2 = 2,097,150

Multiplying the number of subnets times the number of

nodes gives 12,582,900 possible nodes.

Note that this is less than the 16,777,214 possible nodes

that an unsubnetted class A network would have.

Subnetting reduces the number of possible nodes for a given

network, but increases the segmentation of the network.

Classless InterDomain Routing – CIDR

Under CIDR, the subnet mask notation is reduced to a

simplified shorthand. Instead of specifying all of the bits of

the subnet mask, it is simply listed as the number of

contiguous “1”s (bits) in the network portion of the address.

Look at the subnet mask of the above example in binary -

1 2 ... 144 145 146 147 148 149 150 151 152 153 154 ... 200 201

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Enterasys Vertical Horizon VH-2402S2 Spécifications Page 149