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12-19
Cisco IE 2000 Switch Software Configuration Guide
OL-25866-01
Chapter 12 Configuring Switch-Based Authentication
Information About Configuring Switch-Based Authentication
Kerberos Operation
A Kerberos server can be a switch that is configured as a network security server and that can
authenticate remote users by using the Kerberos protocol. Although you can customize Kerberos in a
number of ways, remote users attempting to access network services must pass through three layers of
security before they can access network services.
To authenticate to network services by using a switch as a Kerberos server, remote users must follow
these steps:
1. Authenticating to a Boundary Switch, page 12-19
2. Obtaining a TGT from a KDC, page 12-20
3. Authenticating to Network Services, page 12-20
Authenticating to a Boundary Switch
This section describes the first layer of security through which a remote user must pass. The user must
first authenticate to the boundary switch. This process then occurs:
1. The user opens an un-Kerberized Telnet connection to the boundary switch.
2. The switch prompts the user for a username and password.
3. The switch requests a TGT from the KDC for this user.
Kerberos server A daemon that is running on a network host. Users and network services
register their identity with the Kerberos server. Network services query
the Kerberos server to authenticate to other network services.
KEYTAB
3
A password that a network service shares with the KDC. In Kerberos 5
and later Kerberos versions, the network service authenticates an
encrypted service credential by using the KEYTAB to decrypt it. In
Kerberos versions earlier than Kerberos 5, KEYTAB is referred to as
SRVTAB
4
.
Principal Also known as a Kerberos identity, this is who you are or what a service
is according to the Kerberos server.
Note The Kerberos principal name must be in all lowercase characters.
Service credential A credential for a network service. When issued from the KDC, this
credential is encrypted with the password shared by the network service
and the KDC. The password is also shared with the user TGT.
SRVTAB A password that a network service shares with the KDC. In Kerberos 5
or later Kerberos versions, SRVTAB is referred to as KEYTAB.
TGT Ticket granting ticket that is a credential that the KDC issues to
authenticated users. When users receive a TGT, they can authenticate to
network services within the Kerberos realm represented by the KDC.
1. TGT = ticket granting ticket
2. KDC = key distribution center
3. KEYTAB = key table
4. SRVTAB = server table
Table 12-5 Kerberos Terms (continued)
Term Definition