Concept Guide
TLS_ECDH_RSA_WITH_AES_256_CBC_SHA
TLS_ECDH_RSA_WITH_AES_128_CBC_SHA
TLS_DH_RSA_WITH_AES_256_CBC_SHA
TLS_DH_RSA_WITH_AES_128_CBC_SHA
TLS compression is disabled by default. TLS session resumption is also supported to reduce processor and trac overhead due to public
key cryptographic operations and handshake trac. However, the maximum time allowed for a TLS session to resume without repeating
the TLS authentication or handshake process is congurable with a default of 1 hour. You can also disable session resumption.
Syslog over TLS
Syslog over TLS mandates that a client certicate must be presented, to ensure that all Syslog entries written to the server are from a
trusted client.
Online Certicate Status Protocol (OSCP)
Use the Online Certicate Status Protocol (OSCP) to obtain the revocation status of a X.509v3 certicate.
A device or a Certicate Authority (CAs) can check the status of a X.509v3 certicate by sending an OCSP request to an OCSP server or
responder. An OCSP responder, a server typically run by the certicate issuer, returns a signed response signifying that the certicate
specied in the request is 'good', 'revoked', or 'unknown'. The OCSP response indicates whether the presented certicate is valid.
OCSP provides a way for Certicate Authorities to revoke signed certicates before the expiration date. In a CA certicate, OCSP
Responder information is specied in the authorityInfoAccess extension.
A CA can verify the revocation status of a certicate with multiple OCSP responders. When multiple OCSP responders exist, you can
congure the order or preference the CA takes while contacting various OCSP responders for verication.
Upon receiving a presented certicate, the system sends an OCSP request to an OCSP responder through HTTP. The system then veries
the OCSP response using either a trusted public key or the OCSP responder’s own self-signed certicate. This self-signed certicate
installs on the device's trusted location even before an OCSP request is made. The system accepts or rejects the presented certicate
based on the OCSP response.
In a scenario where all OCSP responders are unreachable, the switch accepts the certicate. This action is the default behavior. You can
also congure an alternate system behavior when all OCSP responders are unreachable. However, the switch may become vulnerable to
denial-of-service attack if you congure the system to deny the certicate when OCSP responders are not reachable.
The system creates logs for the following events:
• Failures to reach OCSP responders
• Invalid OCSP responses—for example, cannot verify the signed response with an installed CA certicate.
• Rejection of a certicate due to OCSP
Conguring OCSP setting on CA
You can congure the CA to contact multiple OCSP servers.
To congure OCSP server for a CA, perform the following step:
In the certicate mode, enter the following command:
ocsp-server URL [nonce] [sign-requests]
1104
X.509v3