Chapter One the foundation of-IP address V1

IP Address

Five classes of IP addresses, just remember 0-127,128-191,192-223,224-239 (multicast), 240-255 (reserved), 127 is the self-ring address, 0.0.0.0 is the network address, 255.255.255.255 is the broadcast address. Private IP three classes, 10.x.x.x,172.16.x.x-172.31.x.x,192.168.x.x.

Sub-network Division

From the point of view of address assignment, the subnet is the extension of the network segment address. In order to make the use of IP address more flexible, only assign IP address network number Net-id, and the subsequent host number Host-id is controlled by this unit.

By subnetting, the entire network address can be divided into more small networks.

Figure 1 IP Address sub-network partitioning
Network Number = "Subnet number =" Host number

When dividing subnets, we must make full use of the address resources, so that the partition of subnets satisfies the requirements of host number.

· Use the variable eldest son netmask vlsm (variable length subnet mask) technology to allocate IP addresses and make full use of address resources.

· for the loopback interface as a device management address, you should try to assign it a separate contiguous address, with a mask of 32 bits.

· for interconnected interfaces between devices, you should try to assign them a separate contiguous address, with a mask of 30 bits.

IP Address borrowing

An IP address is not configured on an interface, but if you want to use it, you can borrow an IP address from another interface that has an IP address so that the interface is working properly.

IP Address Resolution

On Ethernet, the physical address of the host refers to the MAC address. The operation that resolves the hostname to an IP address is done by the DNS server, and the operation that resolves the IP address to the MAC address is done by ARP.

Map of WAN interface IP address and Link layer protocol address

The IP address of the WAN port is mapped to the address of the link layer protocol, such mappings are:

· on the binding relay interface, the IP address is mapped to the DLCI (Data Link Control Identifier).

· on the ATM interface, the IP address is mapped to the pvc/svc.

These mappings can also be called two-time routes. These address mappings need to be configured correctly to ensure that IP services can run on these WAN links.

the IP address space in the vpn-instance can overlap

This article is from the "Digital Kid" blog, please make sure to keep this source http://dcboy.blog.51cto.com/8059630/1794772

Chapter One the foundation of-IP address V1