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This chapter describes how to configure TACACS+ and local authentication to control access to the switch command-line interface (CLI).
This chapter consists of these sections:
These sections describe how the different authentication methods work:
You can configure either or both of these authentication methods to control access to the switch:
When both authentication methods are enabled local authentication is always attempted last. In supervisor engine software release 4.4 and later, you can specify the authentication method to use for console and Telnet connections independently. For example, you might use local authentication for console connections and TACACS+ authentication for Telnet connections.
Local authentication uses locally configured login and enable passwords to authenticate login attempts. The login and enable passwords are local to each switch and are not mapped to individual user names.
Local authentication is enabled by default, but can be disabled if TACACS+ authentication is enabled. If local authentication is disabled and you then disable TACACS+ authentication, local authentication is reenabled automatically.
You can enable local authentication and TACACS+ authentication at the same time. Local authentication is only attempted if TACACS+ authentication fail.
TACACS+ controls access to network devices by exchanging Network Access Server (NAS) information between a network device and a centralized database to determine the identity of a user or entity. TACACS+ is an enhanced version of TACACS, a User Datagram Protocol (UDP)-based access-control protocol specified by RFC 1492. TACACS+ uses TCP to ensure reliable delivery and encrypt all traffic between the TACACS+ server and the TACACS+ daemon on a network device.
TACACS+ works with many authentication types, including fixed password, one-time password, and challenge-response authentication. TACACS+ authentication usually occurs in these instances:
When you request privileged or restricted services, TACACS+ encrypts your user password information using the MD5 encryption algorithm and adds a TACACS+ packet header. This header information identifies the packet type being sent (for example, an authentication packet), the packet sequence number, the encryption type used, and the total packet length. The TACACS+ protocol then forwards the packet to the TACACS+ server.
A TACACS+ server can provide authentication, authorization, and accounting functions. These services, while all part of TACACS+, are independent of one another, so that a given TACACS+ configuration can use any or all of the three services. On the Catalyst 5000 series switches, only the authentication feature is supported.
When the TACACS+ server receives the packet, it does the following:
You can configure a TACACS+ key on the client and server. If you configure a key on the switch, it must be the same as the one configured on the TACACS+ servers. The TACACS+ clients and servers use the key to encrypt all TACACS+ packets transmitted. If you do not configure a TACACS+ key, packets are not encrypted.
You can configure the following TACACS+ parameters on the switch:
TACACS+ authentication is disabled by default. You can enable TACACS+ authentication and local authentication at the same time.
If local authentication is disabled and you then disable TACACS+ authentication, local authentication is reenabled automatically.
Table 15-1 shows the default authentication configuration.
| Feature | Default Value |
|---|---|
Local login authentication (console and Telnet) | Enabled |
Local enable authentication (console and Telnet) | Enabled |
TACACS+ login authentication (console and Telnet) | Disabled |
TACACS+ enable authentication (console and Telnet) | Disabled |
TACACS+ key | None specified |
TACACS+ login attempts | 3 |
TACACS+ server timeout | 5 seconds |
TACACS+ directed request | Disabled |
These guidelines apply when configuring authentication on the switch:
These sections describe how to configure local authentication on the switch:
To enable local authentication on the switch, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable local login authentication on the switch. Use the console or telnet keywords if you want to enable local authentication only for console port or Telnet connection attempts. | set authentication login local enable [console | telnet | both] |
Step 2 Enable local enable authentication on the switch. Use the console or telnet keywords if you want to enable local authentication only for console port or Telnet connection attempts. | set authentication enable local enable [console | telnet | both] |
Step 3 Verify the local authentication configuration. | show authentication |
This example shows how to enable local login and enable authentication for both console and Telnet connections, and how to verify the configuration:
Console> (enable) set authentication login local enable local login authentication set to enable for console and telnet session. Console> (enable) set authentication enable local enable local enable authentication set to enable for console and telnet session. Console> (enable) show authentication Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Console> (enable) show authentication ?
The login password controls access to the user mode CLI.
To set the login password for local authentication, perform this task in privileged mode:
| Task | Command |
|---|---|
Set the login password for access. Enter your old password (press Return on a switch with no password configured), enter your new password, and reenter your new password. | set password |
This example shows how to set the login password on the switch:
Console> (enable) set password Enter old password:<old_password> Enter new password:<new_password> Retype new password:<new_password> Password changed. Console> (enable)
The enable password controls access to the privileged mode CLI.
To set the enable password for local authentication, perform this task in privileged mode:
| Task | Command |
|---|---|
Set the password for privileged mode. Enter your old password (press Return on a switch with no password configured), enter your new password, and reenter your new password. | set enablepass |
This example shows how to set the enable password on the switch:
Console> (enable) set enablepass Enter old password:<old_password> Enter new password:<new_password> Retype new password:<new_password> Password changed. Console> (enable)
 | Caution Make sure that TACACS+ authentication is configured and operating correctly before disabling local login or enable authentication. If you disable local authentication and TACACS+ is not configured correctly, or if the TACACS+ server is not online, you might be unable to log in to the switch. |
To disable local authentication on the switch, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable local login authentication on the switch. Use the console or telnet keywords if you want to disable local authentication only for console port or Telnet connection attempts. | set authentication login local disable [console | telnet | both] |
Step 2 Disable local enable authentication on the switch. Use the console or telnet keywords if you want to disable local authentication only for console port or Telnet connection attempts. | set authentication enable local disable [console | telnet | both] |
Step 3 Verify the local authentication configuration. | show authentication |
This example shows how to disable local login and enable authentication for both console and Telnet connections, and how to verify the configuration (you must have TACACS+ authentication enabled before you disable local authentication):
Console> (enable) set authentication login local disable local login authentication set to disable for console and telnet session. Console> (enable) set authentication enable local disable local enable authentication set to disable for console and telnet session. Console> (enable) show authentication Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local disabled disabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local disabled disabled Console> (enable)
To recover a lost local authentication password, perform this task. You must complete steps 3-7 within 30 seconds or the recovery will fail. If you lost both the login and enable passwords, repeat the process for each password.
Step 1 Connect to the switch through the supervisor engine console port (you cannot recover the password if you are connected through a Telnet connection).
Step 2 Enter the reset system command to reboot the switch.
Step 3 At the "Enter Password" prompt, press Return (the login password is null for 30 seconds when you are connected to the console port).
Step 4 Enter privileged mode using the enable command.
Step 5 At the "Enter Password" prompt, press Return (the enable password is null for 30 seconds when you are connected to the console port).
Step 6 Enter the set password or set enablepass command, as appropriate.
Step 7 When prompted for your old password, press Return.
Step 8 Enter and confirm your new password.
These sections describe how to configure TACACS+ authentication on the switch:
Specify one or more TACACS+ servers before you enable TACACS+ authentication on the switch. The first server you specify is the primary server, unless you explicitly make one server the primary using the primary keyword.
To specify one or more TACACS+ servers, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Specify the IP address of one or more TACACS+ servers. | set tacacs server ip_addr [primary] |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to specify TACACS+ servers and verify the configuration:
Console> (enable) set tacacs server 172.20.52.3 172.20.52.3 added to TACACS server table as primary server. Console> (enable) set tacacs server 172.20.52.7 primary 172.20.52.7 added to TACACS server table as primary server. Console> (enable) set tacacs server 172.20.52.10 172.20.52.10 added to TACACS server table as backup server. Console> (enable) show tacacs Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Tacacs key: Tacacs login attempts: 3 Tacacs timeout: 5 seconds Tacacs direct request: disabled Tacacs-Server Status ---------------------------------------- ------- 172.20.52.3 172.20.52.7 primary 172.20.52.10 Console> (enable)
You can enable TACACS+ authentication for login and enable access to the switch. If desired, you can use the console and telnet keywords to specify that TACACS+ authentication be used only on console or Telnet connections.
To enable TACACS+ authentication, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable TACACS+ authentication for login mode. Use the console or telnet keywords if you want to enable TACACS+ only for console port or Telnet connection attempts. | set authentication login tacacs enable [console | telnet | both] [primary] |
Step 2 Enable TACACS+ authentication for enable mode. Use the console or telnet keywords if you want to enable TACACS+ only for console port or Telnet connection attempts. | set authentication enable tacacs enable [console | telnet | both] [primary] |
Step 3 Verify the TACACS+ configuration. | show tacacs |
This example shows how to enable TACACS+ authentication for console and Telnet connections and how to verify the configuration:
Console> (enable) set authentication login tacacs enable tacacs login authentication set to enable for console and telnet session. Console> (enable) set authentication enable tacacs enable tacacs enable authentication set to enable for console and telnet session. Console> (enable) show authentication Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Console> (enable)
This example shows how to enable TACACS+ authentication for Telnet connections only and how to verify the configuration:
Console> (enable) set authentication login tacacs enable telnet tacacs login authentication set to enable for telnet session. Console> (enable) set authentication enable tacacs enable telnet tacacs enable authentication set to enable for telnet session. Console> (enable) show authentication Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs disabled enabled(primary) local enabled(primary) enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs disabled enabled(primary) local enabled(primary) enabled Console> (enable)
To specify the TACACS+ key, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure the key used to encrypt packets. | set tacacs key key |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to specify the TACACS+ key and verify the configuration:
Console> (enable) set tacacs key Secret_String The tacacs key has been set to Secret_String. Console> (enable) show tacacs Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Tacacs key: Secret_String Tacacs login attempts: 3 Tacacs timeout: 5 seconds Tacacs direct request: disabled Tacacs-Server Status ---------------------------------------- ------- 172.20.52.3 172.20.52.7 primary 172.20.52.10 Console> (enable)
You can specify the timeout interval between retransmissions to the TACACS+ server. The default timeout is 5 seconds.
To specify the TACACS+ timeout interval, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure the TACACS+ timeout interval. | set tacacs timeout seconds |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to set the server timeout interval and verify the configuration:
Console> (enable) set tacacs timeout 30 Tacacs timeout set to 30 seconds. Console> (enable) show tacacs Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Tacacs key: Secret_String Tacacs login attempts: 3 Tacacs timeout: 30 seconds Tacacs direct request: disabled Tacacs-Server Status ---------------------------------------- ------- 172.20.52.3 172.20.52.7 primary 172.20.52.10 Console> (enable)
You can specify the number of failed login attempts allowed.
To specify the number of login attempts allowed, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Configure the number of allowed login attempts. | set tacacs attempts number |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to set the number of login attempts and verify the configuration:
Console> (enable) set tacacs attempts 5 Tacacs number of attempts set to 5. Console> (enable) show tacacs Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Tacacs key: Secret_String Tacacs login attempts: 5 Tacacs timeout: 30 seconds Tacacs direct request: disabled Tacacs-Server Status ---------------------------------------- ------- 172.20.52.3 172.20.52.7 primary 172.20.52.10 Console> (enable)
When TACACS+ directed request is enabled, users must specify the hostname of a configured TACACS+ server (in the form username@server_hostname) or the authentication request will fail after the @ sign.
To enable TACACS+ directed request, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Enable TACACS+ directed request on the switch. | set tacacs directedrequest enable |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to enable TACACS+ directed request and verify the configuration:
Console> (enable) set tacacs directedrequest enable Tacacs direct request has been enabled. Console> (enable) show tacacs Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs enabled(primary) enabled(primary) local enabled enabled Tacacs key: Secret_String Tacacs login attempts: 5 Tacacs timeout: 30 seconds Tacacs direct request: enabled Tacacs-Server Status ---------------------------------------- ------- 172.20.52.3 172.20.52.7 primary 172.20.52.10 Console> (enable)
To disable TACACS+ directed request, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable TACACS+ directed request on the switch. | set tacacs directedrequest disable |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to disable TACACS+ directed request:
Console> (enable) set tacacs directedrequest disable Tacacs direct request has been disabled. Console> (enable)
To clear one or more TACACS+ servers, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Specify the IP address of the TACACS+ server to clear from the configuration. Use the all keyword to clear all of the servers from the configuration. | clear tacacs server [ip_addr | all] |
Step 2 Verify the TACACS+ server configuration. | show tacacs |
This example shows how to clear a TACACS+ server from the configuration:
Console> (enable) clear tacacs server 172.20.52.3 172.20.52.3 cleared from TACACS table Console> (enable)
To clear the TACACS+ key, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Clear the TACACS+ key. | clear tacacs key |
Step 2 Verify the TACACS+ configuration. | show tacacs |
This example shows how to clear the TACACS+ key:
Console> (enable) clear tacacs key TACACS server key cleared. Console> (enable)
If local authentication is disabled and you disable TACACS+ authentication, local authentication is automatically enabled on the switch.
To disable TACACS+ authentication, perform this task in privileged mode:
| Task | Command |
|---|---|
Step 1 Disable TACACS+ authentication for login mode. Use the console or telnet keywords if you want to disable TACACS+ only for console port or Telnet connection attempts. | set authentication login tacacs disable [console | telnet | both] |
Step 2 Disable TACACS+ authentication for enable mode. Use the console or telnet keywords if you want to disable TACACS+ only for console port or Telnet connection attempts. | set authentication enable tacacs disable [console | telnet | both] |
Step 3 Verify the TACACS+ configuration. | show tacacs |
This example shows how to disable TACACS+ authentication for console and Telnet connections and how to verify the configuration:
Console> (enable) set authentication login tacacs disable tacacs login authentication set to disable for console and telnet session. Console> (enable) set authentication enable tacacs disable tacacs enable authentication set to disable for console and telnet session. Console> (enable) show authentication Login Authentication: Console Session Telnet Session --------------------- ---------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Enable Authentication: Console Session Telnet Session ---------------------- ----------------- ---------------- tacacs disabled disabled local enabled(primary) enabled(primary) Console> (enable)
Posted: Tue Mar 30 16:01:50 PST 1999
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