3Com Switch 4210 9-Port, Руководство по настройке

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Configuring IP Addresses 89
While allowing you to create multiple logical networks within a single Class A, B,
or C network, subnetting is transparent to the rest of the Internet. All these
networks still appear as one. As subnetting adds an additional level, subnet ID, to
the two-level hierarchy with IP addressing, IP routing now involves three steps:
delivery to the site, delivery to the subnet, and delivery to the host.
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 of 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-ones host ID is the broadcast address and the other with an all-zeros 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 Ðó 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
Switch 4210 Family support assigning IP addresses to VLAN interfaces and
loopback interfaces. Besides directly assigning an IP address to a VLAN interface,
you may configure a VLAN interface to obtain an IP address through BOOTP or
DHCP 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.
n
This chapter only covers how to assign an IP address manually. For the other two
approaches to IP address assignment, refer to “DHCP Overview” on page 281 and
subsequent chapters.
n
■
A newly specified IP address overwrites the previous one if there is any.
■
The IP address of a VLAN interface must not be on the same network segment
as that of a loopback interface on a device.
Table 49 Configure an IP address to an interface
Operation 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 } [ sub ]
Required
No IP address is assigned by
default.