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Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
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Chapter 38 Configuring IP Unicast Routing
Configuring IP Addressing
Assigning IP Addresses to Network Interfaces
An IP address identifies a location to which IP packets can be sent. Some IP addresses are reserved for
special uses and cannot be used for host, subnet, or network addresses. RFC 1166, “Internet Numbers,”
contains the official description of IP addresses.
An interface can have one primary IP address. 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 referred to as a subnet mask.
To receive an assigned network number, contact your Internet service provider.
Beginning in privileged EXEC mode, follow these steps to assign an IP address and a network mask to
a Layer 3 interface:
Use of Subnet Zero
We strongly discourage subnetting with a subnet address of zero because of the problems that can arise
if a network and a subnet have the same addresses. For example, if network 131.108.0.0 is subnetted as
255.255.255.0, subnet zero would be written as 131.108.0.0, which is the same as the network address.
You can use the all ones subnet (131.108.255.0) and, even though we discourage this practice, you can
enable the subnet zero if you need the entire subnet space for your IP address.
Beginning in privileged EXEC mode, follow these steps to enable subnet zero:
Use the
no ip subnet-zero
global configuration command to restore the default and to disable the use of
subnet zero.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
interface
interface-id
Enter interface configuration mode, and specify the Layer 3
interface to configure.
Step 3
no switchport
Remove the interface from Layer 2 configuration mode (if it is a
physical interface).
Step 4
ip address
ip-address
subnet-mask
Configure the IP address and IP subnet mask.
Step 5
no shutdown
Enable the interface.
Step 6
end
Return to privileged EXEC mode.
Step 7
show interfaces
[
interface-id
]
show ip interface
[
interface-id
]
show running-config interface
[
interface-id
]
Verify your entries.
Step 8
copy running-config startup-config
(Optional) Save your entries in the configuration file.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
ip subnet-zero
Enable the use of subnet zero for interface addresses and routing updates.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
Verify your entry.
Step 5
copy running-config startup-config
(Optional) Save your entry in the configuration file.
