Command Reference IP Address Commands
to different networks, and different secondary IP addresses must also belong to different networks.
Secondary IP addresses are often used in network construction. Typically, you can try to use
secondary IP addresses in the following situations:
A network does not have enough host addresses. At present, a LAN should be a class C network
where 254 hosts can be configured. However, when there are more than 254 hosts in the LAN,
another class C network address is necessary since one class C network is not enough. Therefore,
the device should be connected to two networks and multiple IP addresses should be configured.
Many older networks are L2-based bridge networks that have not been divided into different subnets.
Use of secondary IP addresses will make it very easy to upgrade this network to an IP layer-based
routing network. The equipment is configured with an IP address for each subnet.
Two subnets of a network are separated by another network. You can create a subnet for the
separated network, and connect the separated subnet by configuring a secondary IP address. One
subnet cannot appear on two or more interfaces of a device.
In general, the Layer-2 switch is configured with a default gateway by using the ip default-gateway
command. Sometimes the Layer-2 switch may be managed through Telnet, and the management IP
address and default gateway of the Layer-2 switch need to be modified. In this case, after configuring
either of the ip address and ip default-gateway commands, the other command cannot be
configured any more due to the configuration change which causes a failure to access this device
through the network. So you need to use the keyword gateway in the ip address command to modify
both the management IP address and the default gateway. The keyword gateway is not in the output
of the show running config command but in the output of the ip default-gate command.
Configuration
Examples
The following example sets the primary IP address to 10.10.10.1, and the network mask to
255.255.255.0.
ip address 10.10.10.1 255.255.255.0
The following example sets the default gateway to 10.10.10.254.
ip address 10.10.10.1 255.255.255.0 gateway 10.10.10.254
Related
Commands
Command Description
show interface
Shows detailed information about the
interface.
Platform
Description
For the Layer 2 switch, the IP address can be configured only for a Layer 3 interface. The Level-2
address is not supported, that is, the secondary IP address option is unavailable.
The keyword gateway is only supported by Layer-2 switches.
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