<｜begin▁of▁sentence｜>
### Instruction:
How does Cisco IOS XR support external AAA for user authentication?
### Response:
Cisco IOS XR supports external Authentication, Authorization and Accounting (AAA) using TACACS+ and RADIUS protocols. The router can be configured to authenticate users against an external AAA server. This allows centralized management of user credentials.
<|EOT|>
