3com 5500-ei pwr Installation Instruction

 

1-3 

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 × 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.  

S5500-EI 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.  

 

This chapter only covers how to assign an IP address manually. For the other two approaches to IP 

address assignment, refer to the part discussing DHCP in this manual.  

 

Follow these steps to configure an IP address to an interface: 

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.