Which action is a valid fallback when a client certificate is unavailable during SMTP authentication on Cisco ESA?
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A. B. C. D.B.
https://www.cisco.com/c/en/us/td/docs/security/esa/esa12-0/user_guide/b_ESA_Admin_Guide_12_0/When a client attempts to authenticate to an SMTP server using client certificates, the server verifies the client's identity by checking the validity of the certificate. However, there are times when the client certificate is not available, which can be due to various reasons such as the certificate being expired or revoked or the client not presenting the certificate during the authentication process. In such cases, the server may need to use an alternative method to authenticate the client.
In the context of Cisco Email Security Appliance (ESA), the fallback method to use when a client certificate is unavailable during SMTP authentication depends on the configuration of the ESA. The four options listed in the answer choices are all valid methods that can be used for authentication, but they differ in their purpose and configuration.
Here's a brief overview of each option:
A. LDAP Query: This method involves querying an LDAP server to retrieve the user's credentials and authenticate the user based on those credentials. The ESA can be configured to use LDAP for authentication as a fallback method when a client certificate is not available.
B. SMTP AUTH: This method involves authenticating the user using the SMTP AUTH command, which allows the user to send a username and password to the server for authentication. This method can be used as a fallback when client certificates are not available.
C. SMTP TLS: This method involves using Transport Layer Security (TLS) to encrypt the SMTP connection between the client and the server. TLS can also be used to authenticate the client using client certificates, but it can also be used as a fallback method for authentication when certificates are not available.
D. LDAP BIND: This method involves binding to an LDAP directory using the user's credentials to authenticate the user. This method can be used as a fallback when client certificates are not available.
In summary, all of the options listed are valid fallback methods that can be used for authentication when client certificates are not available on Cisco ESA. The specific method chosen depends on the configuration of the ESA and the preferences of the administrator.