Shulou(Shulou.com)06/01 Report--

As a result of doing idc after-sales, now contact with some network ip and subnetting, abcd classless address of some division, a simple look. Write down the main points

The network address portion of the IP address cannot be set to all 1s or all zeros.

The subnet portion of the IP address cannot be set to all 1s or all zeros.

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

Network 1 2 7. X. X. X cannot be used as a network address.

1. Network address

When all bits in the host address in the IP address are set to 0, it indicates a network, not on which network

The specific host of the. These types of entries can usually be found in the routing table because the router controls communication between networks.

Traffic, rather than traffic between individual hosts.

The network bits cannot all be 0, because 0 is an illegal network address and is used to represent the unknown network.

Contact or address ".

4. Broadcast to all hosts

If all host bits in the IP address are set to 1, this will be interpreted as a broadcast to all hosts in that network.

An example is 1, 3, 2. 1 0 0. 2 5 5. 2 55 or 200. 2 0 0. 1 5 0. 2 5 5 .

At this time, the host bit would like to say that in category a, the network address is the first eight bits, and the number of hosts is the last 24 bits.

2. Category B

In the class B address, 16 bits are assigned to the network address and 16 bits are assigned to the host address. A class B address can be used as 1.

The first two bits of the 8-bit group are identified as 10. The corresponding values range from 1.28 to 1.91. Now that the first two are pre-defined, the actual

1 4 bits are left for the network address, so the possible combination produces 1 6, 3 8 3 networks, each containing 6 5 5 3 5

Mainframe.

3. Category C

Class C divides the network address into 24 bits and leaves 8 bits for the host address. The first 3 bits of the first 8 bits of a Class C address are 11 0.

The corresponding decimal number ranges from 1 9 2 to 2 23. In Class C addresses, only the last 8 bits are used for host addresses, which limits the

Each network can only have a maximum of 254 hosts. Since the network number has 21 digits available (3 digits have been pre-set to 11 0)

There are 209 7 151 possible networks.

4. Category D

Class D addresses start with 111 0. The octet represented by this ranges from 22.4 to 23.9. These addresses are not used for standard I P addresses.

Instead, a class D address refers to a group of hosts that are registered as members of a multicast team. Multicast teams and e-mail

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

The multicast address sends data to some hosts. Multicast requires a special routing configuration; by default, it does not

It will be forwarded.

5. Category E

If the first four bits of the first 8-bit group are all set to 1111, the address is a Class E address. The range of these addresses is

240 ~ 254.

The above picture can describe what is written above, and it is easier to understand with reference to this picture.

This reference is Cisco's ip configuration document.

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