The network administrator performs the configuration shown in the following figure on RT A If a user needs to be authenticated in the authentication domain named huawei, which of the following statements is true?

In the domain view the command sequence first specifies “authentication-scheme aul”; the subsequent “backup-authentication-scheme au2” (or equivalent) designates au2 as the standby method. The router always tries the primary scheme (aul); only if that scheme is removed from the configuration does the domain fall back to its defined backup scheme (au2).

A. au2 is only the backup scheme, used only when aul is absent.
B. aul, not au1, is configured as primary in the domain.
C. au2 is not attempted while aul exists; deletion order matters.

7. Huawei AR Series Access Devices Configuration Guide – User Access and Authentication, V300R019C10, Sect.2.3 “Configuring an Authentication Domain”, p.28-29 (example with ‘authentication-scheme’ and ‘backup-authentication-scheme’).

8. Huawei AAA Command Reference, V300R019C10, “domain authentication-scheme/backup-authentication-scheme”, para.1-2.