It
is important to note that the network transfer efficiency can be improved by not assigning different IP addresses to computers on the same network. In fact, computers within the same network are still in the same broadcast domain, the number of broadcast packets will not be reduced due to the different IP addresses, so only to specify a different network segment for the computer, and can not achieve the purpose of dividing the broadcast domain. To reduce the broadcast domain, the most fundamental solution is to divide the VLAN, and then specify a different IP network segment for each VLAN.
The disadvantage of traditional IP address classification is that it is not possible to use routing within the network, so that for larger networks, such as a Class A network, it becomes difficult to manage because the number of hosts in the network is too large. To this end, a subnet mask (NetMask) is introduced to logically divide a large network into small networks. A subnet mask consists of a series of 1 and 0 that indicate what the network number of an IP address is by doing a "and" operation with the IP address. For traditional IP address classifications, the subnet mask for Class A addresses is the subnet mask for the 255.0.0.0;b class address is the subnet mask for the 255.255.0.0;c class address is 255.255.255.0. For example, if you want to divide a class B network 166.111.0.0 into multiple Class C subnets, just set its subnet mask to 255.255.255.0, so that 166.111.1.1 and 166.111.2.1 belong to different networks. As such, the method of dividing a network into multiple networks through longer subnet masks is called subnetting (subnetting).
when choosing a private (private) IP address, you should be aware of the following points:
1, for each network segment is assigned a class C IP address segment, we recommend the use of 192.168.2.0--192.168.254.0 segment IP address. Because some network devices, such as broadband routers or wireless routers, or applications (such as ICS) have auto-assigned IP address capabilities, and the default IP address pool is often located in 192.168.0.0 and 192.168.1.0, so when this IP address segment is used, it is often easy to cause IP address collisions or other failures. Therefore, unless necessary, the use of the above two class C address segments should be avoided as far as possible.
2, can adopt the C-Class address subnet mask, if necessary, can be used to change the eldest son Netmask. In general, do not use an oversized subnet mask, no more than 250 computers per network segment. The greater the number of computers in the same segment, the greater the number of broadcast packets, the more loss of effective bandwidth, and the lower the network transmission efficiency.
3. Even with 10.0.0.1--10.255.255.254 or 172.16.0.1--172.31.255.254 segment IP addresses, it is recommended that you use 255.255.255.0 as the subnet mask to obtain more IP segments and to have fewer computers in each subnet. Of course, if necessary, can be used to change the eldest son netmask, the appropriate increase in the number of computers can accommodate.
4, for network equipment management WLAN allocation of a separate IP address segment to avoid the occurrence of network device management IP address conflicts, thereby affecting the implementation of remote management. For the same reason, all servers must also be partitioned into a separate network segment. A
supernetting is a concept similar to a subnet, which synthesizes multiple small networks into a large network with a shorter subnet mask. For example, a unit is divided into 8 class C addresses: 202.120.224.0 ~ 202.120.231.0, as long as its subnet mask is set to 255.255.248.0, you can make these C-type networks communicate.
due to the explosive growth of host number on Internet, the defect of traditional IP address classification makes a large number of vacant IP address waste, resulting in the lack of IP address resource, and the increase of network number makes the routing table too large and difficult to manage. For many companies with hundreds of hosts, assigning a class B address is too wasteful, and assigning a class C address is not enough, so you can only assign multiple class C addresses, but this exacerbates the expansion of the routing table. In this context, there is a non-class inter-domain routing (cidr,classless inter-domain Routing) to solve this problem. In CIDR, the address is allocated according to the network topology, and a contiguous set of network addresses can be assigned to a company and the entire set of addresses as a network address (for example, using the Hyper-network technology), with only one routing table entry on the external routing table. This solves the problem of address scarcity, and solves the problem of routing table bloat. In addition, CIDR divides the entire world into four regions, assigning each region a contiguous class C address, namely: Europe (194.0.0.0~195.255.255.255), North America (198.0.0.0~199.255.255.255), Central and South America ( 200.0.0.0~201.255.255.255) and Asia Pacific (202.0.0.0~203.255.255.255). In this way, when a router outside the Asia Pacific region receives the first 8 bits of 202 or 203 of the data, it only needs to be placed in the route to the Asia-Pacific region, while the last 24-bit routing can be processed after the datagram arrives in the Asia-Pacific region, which greatly alleviates the problem of routing table bloat.
Routing between subnets, hyper-grids, and non-class domains
