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Configuring IP Addressing
Assigning IP Addresses to Network Interfaces
IPC-8
Cisco IOS IP Configuration Guide
The official description of IP addresses is found in RFC 1166, Internet Numbers.
To receive an assigned network number, contact your Internet service provider (ISP).
An interface can have one primary IP address. To assign a primary IP address and a network mask to a
network interface, use the following command in interface configuration mode:
A mask identifies the bits that denote the network number in an IP address. When you use the mask to
subnet a network, the mask is then referred to as a subnet mask.
Note We only support network masks that use contiguous bits that are flush left against the network field.
The tasks to enable or disable additional, optional, IP addressing features are contained in the following
sections:
• Assigning Multiple IP Addresses to Network Interfaces
• Enabling Use of Subnet Zero
• Disabling Classless Routing Behavior
• Enabling IP Processing on a Serial Interface
Table 3 Reserved and Available IP Addresses
Class Address or Range Status
A 0.0.0.0
1.0.0.0 to 126.0.0.0
127.0.0.0
Reserved
Available
Reserved
B 128.0.0.0 to 191.254.0.0
191.255.0.0
Available
Reserved
C 192.0.0.0
192.0.1.0 to 223.255.254
223.255.255.0
Reserved
Available
Reserved
D 224.0.0.0 to 239.255.255.255 Multicast group addresses
E 240.0.0.0 to 255.255.255.254
255.255.255.255
Reserved
Broadcast
Command Purpose
Router(config-if)# ip address ip-address mask
Sets a primary IP address for an interface.