The subnet mask partition is handy to remember

Because do IDC after sale, now contact some network IP and subnet division, ABCD no class address of some division, simple look. Write the key.

The network address portion of the IP address cannot be set to either "All 1" or "all 0".

The subnet portion of the IP address cannot be set to "all 1" or "all 0".

The host address portion of the IP address cannot be set to all 1 or all 0.

Network 1 2 7. X. X. x cannot be a network address.

1. Network Address

When all the bits in the host address in the I P address are set to 0 o'clock, it is indicated as a network and not on which network

The specific host. These types of entries can usually be found in the routing table because routers control the network

Volume, rather than the amount of traffic between individual hosts.

The network bit cannot be all 0 because 0 is an illegal network address and is used to represent an "unknown network

Contact or address ".

4. Broadcast for all hosts

If all the host bits in the I p address are set to 1, this is interpreted as a broadcast for all hosts in that network.

Examples such as 1 3 2. 1 0 0. 2 5 5. 2 5 5 or 2 0 0. 2 0 0. 1 5 0. 2 5 5.

Host bit at this point to say a class is the network address is the first eight bits, the number of hosts is the last 24 bits,

2. Class B

Class B address, the network address is assigned 1 6 bits, the host address is assigned 1 6 bits, a Class B address can be used 1th

The first two bits of a 8-bit group are identified with 1 zero. This corresponds to a value from 1 2 8 to 1 9 1. Since the first two have been pre-defined, the actual

There are 1 4 bits left on the network address, so the possible combination produces 1 6, 3 8 3 networks, and each network contains 6 5 5 3 5

Host.

3. Class C

The C class has 2 4 bits for the network address, leaving 8 bits for the host address. The first 3 bits of the first 8-bit group of Class C addresses are 11 0,

This corresponds to the decimal number from 1 9 2 to 2 2 3. In class C addresses, only the last 8-bit group is used for the host address, which limits

Each network can have a maximum of only 2 5 4 hosts. Since the network number is 2 1 bits can be used (3 bits are pre-set to 11 0),

There is a total of 2 0 9 7 1 5 1 possible networks.

4. Class D

Class D addresses start at 111 0. This represents a eight-bit group from 2 2 4 ~ 2 3 9. These addresses are not used for standard I P addresses.

Instead, a Class D address refers to a set of hosts that are registered as members of the multicast team. Multicast teams and email

The allocation list is similar. Just as you can use the Assign list to publish a message to some people, you can

Multicast addresses send data to some hosts. Multicast requires a special routing configuration; By default, it does not

will be forwarded.

5. Class E

If the first 4 bits of a 1th 8-bit group are set to 1111, the address is an e-class address. The ranges for these addresses are

2 4 0 ~ 2 5 4.

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This article references the IP configuration documentation for Cisco

This article is from the "Li Jingxiang" blog, make sure to keep this source http://9283898.blog.51cto.com/9273898/1688456

The subnet mask partition is handy to remember