H3C Technologies H3C S5120 Series Switches - Manual (Page 212)

1-3
In the absence of subnetting, some special addresses such as the addresses with the net ID of all zeros
and the addresses with the host ID of all ones, are not assignable to hosts. The same is true for
subnetting. When designing your network, you should note that subnetting is somewhat a tradeoff
between 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 address
and the other with an all-zero host ID is the network address) hosts before being subnetted. After you
break it down into 512 (2
9
) subnets by using the first 9 bits of the host ID for the subnet, you have only 7
bits for the host ID and thus have only 126 (2
7
– 2) hosts in each subnet. The maximum number of hosts
is 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 natural
masks): 255.0.0.0, 255.255.0.0, and 255.255.255.0 respectively.
Configuring IP Addresses
An interface can communicate with other hosts after it obtains an IP address. Besides directly assigning
an 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, from
manual assignment to BOOTP for example, the IP address obtained from BOOTP will overwrite the old
one manually assigned.
This chapter only covers how to assign an IP address manually. For how to obtain an IP address
through BOOTP or DHCP, refer to DHCP Configuration .
Assigning an IP Address to an Interface
Follow these steps to assign an IP address to an interface:
To do… Use the command… Remarks
Enter system view system-view ––
Enter interface view
interface interface-type
interface-number
––
Assign an IP address to
the interface ip address ip-address { mask |
mask-length }
Required
No IP address is assigned by
default.