Assign an IP Address to a Loopback Interface

IP addresses can be assigned to a loopback interface, using Classless Interdomain Routing (CIDR) network masks. Loopback interfaces add stability to a network, because they do not incur route flap problems due to unstable links between devices.

About this task

IPv4 routing is enabled by default on SLX-OS devices that operate at Layer 3 and cannot be disabled. IP addresses must be assigned to interfaces on the devices to allow IPv4-based protocols to operate across the network.

Procedure

From privileged EXEC mode, access global configuration mode.
```
device# configure terminal
```
Access the interface to which you are assigning the IP addresses.
```
device(config)# interface loopback 1
```
Assign an IP address to the interface.
Note
You can define only one IP address per loopback. The only valid mask value is /32.
```
device(config-Loopback-1)# ip address 1.1.1.1/32
```
Activate the interface.
```
device(config-Loopback-1)# no shutdown
```

Verify that the IP address is assigned to the interface.

device(config-Loopback-1)# do show ip interface loopback 1
 Loopback 1 is up protocol is up
 Primary Internet Address is 1.1.1.1/32
 IP MTU is 1500
 Proxy Arp is not Enabled
 ICMP unreachables are always sent
 ICMP mask replies are never sent
 IP fast switching is enabled
 Vrf : default-vrf