1-3In the absence of subnetting, some special addresses such as the addresses with the net ID of all zerosand the addresses with the host ID of all ones, are not assignable to hosts. The same is true forsubnetting. When designing your network, you should note that subnetting is somewhat a tradeoffbetween subnets and accommodated hosts. For example, a Class B network can accommodate 65,534(2 16 – 2. Of the two deducted Class B addresses, one with an all-one host ID is the broadcast addressand the other with an all-zero host ID is the network address) hosts before being subnetted. After youbreak it down into 512 (29) subnets by using the first 9 bits of the host ID for the subnet, you have only 7bits for the host ID and thus have only 126 (27 – 2) hosts in each subnet. The maximum number of hostsis thus 64,512 (512 × 126), 1022 less after the network is subnetted.Class A, B, and C networks, before being subnetted, use these default masks (also called naturalmasks): 255.0.0.0, 255.255.0.0, and 255.255.255.0 respectively.Configuring IP AddressesAn interface can communicate with other hosts after it obtains an IP address. Besides directly assigningan IP address to an interface, you may configure the interface to obtain one through BOOTP, DHCP,address negotiation as alternatives. If you change the way an interface obtains an IP address, frommanual assignment to BOOTP for example, the IP address obtained from BOOTP will overwrite the oldone manually assigned.This chapter only covers how to assign an IP address manually. For how to obtain an IP addressthrough BOOTP or DHCP, refer to DHCP Configuration .Assigning an IP Address to an InterfaceFollow these steps to assign an IP address to an interface:To do… Use the command… RemarksEnter system view system-view ––Enter interface view interface interface-typeinterface-number ––Assign an IP address tothe interfaceip address ip-address { mask |mask-length }RequiredNo IP address is assigned bydefault.
