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### Instruction:
How to configure a loopback interface?
### Response:
To configure a loopback interface in Cisco IOS XR, use the 'interface Loopback' command in global configuration mode. RP/0/RP0/CPU0:router(config)#interface Loopback0
RP/0/RP0/CPU0:router(config-if)#ipv4 address 10.1.1.1 255.255.255.255
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