To specify the certificate revocation list (CRL) query and CRL cache options for the public key infrastructure (PKI) trustpool, use the crl command in ca-trustpool configuration mode. To return to the default behavior in which the router checks the URL that is embedded in the certificate, use the no form of this command.
Before you can configure this command, you must enable the crypto pki trustpool policy command, which enters ca-trustpool configuration mode.
The crl query command is used if the CDP is in Lightweight Directory Access Protocol (LDAP) form, which means that the CDP location in the certificate indicates only where the CRL distribution point (CDP) is located in the directory; that is, the CDP does not indicate the actual query location for the directory.
The Cisco IOS software queries the CRL to ensure that the certificate has not been revoked in order to verify a peer certificate (for example, during Internet Key Exchange (IKE) or Secure Sockets Layer (SSL) handshake). The query looks for the CDP extension in the certificate, which is used to download the CRL. If this query is unsuccessful, then the Simple Certificate Enrollment Protocol (SCEP) GetCRL mechanism is used to query the CRL from the CA server directly (some CA servers do not support this method).
Cisco IOS software supports the following CDP entries:
HTTP URL with a hostname. For example: http://myurlname/myca.crl
HTTP URL with an IPv4 address. For example: http://10.10.10.10:81/myca.crl
LDAP URL with a hostname. For example: ldap://CN=myca, O=cisco
LDAP URL with an IPv4 address. For example: ldap://10.10.10.10:3899/CN=myca, O=cisco
LDAP/X.500 DN. For example: CN=myca, O=cisco
The Cisco IOS needs a complete URL in order to locate the CDP.