Configuring Ip Addresses - H3C S3100 8C SI Operation Manual

Operation Manual –IP Address-IP Performance
H3C S3100 Series Ethernet Switches
Figure 1-2
Figure 1-2 Subnet a Class B network
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
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
subnet, you have only 7 bits for the host ID and thus have only 126 (2
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.

1.2 Configuring IP Addresses

S3100 Series Ethernet Switches 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.
shows how a Class B network is subnetted.
9
) subnets by using the first 9 bits of the host ID for the
Chapter 1 IP Addressing Configuration
1-3
16
– 2. Of the two deducted
7
– 2) hosts in