3com S7906E Manuel De Montage

 

1-2 

Table 1-1 IP address classes and ranges 

A 

0.0.0.0 to 
127.255.255.255 

The IP address 0.0.0.0 is used by a host at bootstrap for 
temporary communication. This address is never a valid 
destination address.  

Addresses starting with 127 are reserved for loopback test. 
Packets destined to these addresses are processed locally 
as input packets rather than sent to the link.  

B 

128.0.0.0 to 
191.255.255.255 

–– 

C 

192.0.0.0 to 
223.255.255.255 

–– 

D 

224.0.0.0 to 
239.255.255.255 

Multicast addresses. 

E 

240.0.0.0 to 
255.255.255.255 

Reserved for future use except for the broadcast address 
255.255.255.255.  

 

The following IP addresses are for special use, and they cannot be used as host IP addresses: 

z 

IP address with an all-zero net ID: Identifies a host on the local network. For example, IP address 

0.0.0.16 indicates the host with a host ID of 16 on the local network. 

z 

IP address with an all-zero host ID: Identifies a network. 

z 

IP address with an all-one host ID: Identifies a directed broadcast address. For example, a packet 

with the destination address of 192.168.1.255 will be broadcasted to all the hosts on the network 

192.168.1.0. 

Subnetting was developed to address the risk of IP address exhaustion resulting from fast expansion of 

the Internet. The idea is to break a network down into smaller networks called subnets by using some 

bits of the host ID to create a subnet ID. To identify the boundary between the host ID and the 

combination of net ID and subnet ID, masking is used. 

Each subnet mask comprises 32 bits related to the corresponding bits in an IP address. In a subnet 

mask, the part containing consecutive ones identifies the combination of net ID and subnet ID whereas 

the part containing consecutive zeros identifies the host ID. 

 shows how a Class B network is subnetted. 

Figure 1-2 Subnet a Class B network