8-33
Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 8 Configuring Switch-Based Authentication
Controlling Switch Access with Kerberos
Kerberos Operation
A Kerberos server can be a Cisco ME 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 Cisco ME switch as a Kerberos server, remote users must
follow these steps:
1.
Authenticating to a Boundary Switch, page 8-33
2.
Obtaining a TGT from a KDC, page 8-34
3.
Authenticating to Network Services, page 8-34
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.
4.
The KDC sends an encrypted TGT that includes the user identity to the switch.
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 8-2
Kerberos Terms (continued)
Term
Definition
