Authentication verifies the identity of a user, device, client, or communicating entity before access is granted. It answers, “Who are you?” and forms the first part of AAA, alongside authorization and accounting. section 11.4.1 section 11.4
Authentication appears in several operational forms:
- AAA authenticates users or systems, then separates identity verification from permissions and activity tracking. section 11.4.1
- FTP uses a username and password configured on the Cisco device, matching an account on the FTP server. section 8.2.2
- SNMPv3 authenticates users with passwords protected by hashing algorithms; authentication may be combined with encryption through AuthPriv. section 6.3.2
- REST APIs support basic credentials, bearer tokens, API keys, and OAuth 2.0; successful authentication still requires sufficient authorization. section 23.3.2
FTP image transfer
A Cisco switch initially fails to retrieve an IOS image with “Incorrect Login/Password.” Configuring `ip ftp username jeremy` and `ip ftp password password123` supplies default credentials; the subsequent `copy ftp: flash:` succeeds and `show flash:` confirms the new image.
R1(config)# snmp-server group GROUP1 v3 priv #1 R1(config)# snmp-server user USER1 GROUP1 v3 auth sha AuthPW priv aes 256 PrivPW #2 #1 Creates a group with AuthPriv security #2 Creates a user account (USER1) in the GROUP 1 group
Use the Cisco IOS commands to see how an SNMPv3 group selects AuthPriv and how a user is assigned to that group. section 6.3.2
