AAA Authorization and Authentication Cache

RADIUS and TACACS+ clients run on Cisco routers and send authentication requests to a central RADIUS or TACACS+ server that contains all user authentication and network service access information. The router is required to communicate with an offload RADIUS or TACACS+ server to authenticate a given call and then apply a policy or service to that call. Unlike authentication, authorization, and accounting (AAA) accounting, AAA authentication and authorization is a blocking procedure, which means the call setup may not proceed while the call is being authenticated and authorized. Thus, the time required to process the call setup is directly impacted by the time required to process such an authentication or authorization request from the router to the offload RADIUS or TACACS+ server, and back again. Any communication problems in the transmission, offload server utilization, and numerous other factors cause significant degradation in a router's call setup performance due simply to the AAA authentication and authorization step. The problem is further highlighted when multiple AAA authentications and authorizations are needed for a single call or session.

A solution to this problem is to minimize the impact of such authentication requests by caching the authentication and authorization responses for given users on the router, thereby removing the need to send the requests to an offload server again and again. This profile caching adds significant performance improvements to call setup times. Profile caching also provides an additional level of network reliability because user and service profiles that are returned from authentication and authorization responses can be queried from multiple sources and need not depend solely on an offload server.

To take advantage of this performance optimization, you need to configure the authentication method list so that the AAA cache profile is queried first when a user attempts to authenticate to the router. See the Method Lists in Authorization and Authentication Profile Caching section for more information.

If, for whatever reason, RADIUS or TACACS+ servers are unable to provide authentication and authorization responses, network users and administrators can be locked out of the network. The profile caching feature allows usernames to be authorized without having to complete the authentication phase. For example, a user by the name of user100@example.com with a password secretpassword1 could be stored in a profile cache using the regular expression ".*@example.com". Another user by the name of user101@example.com with a password of secretpassword2 could also be stored using the same regular expression, and so on. Because the number of users in the ".*@example.com" profile could number in the thousands, it is not feasible to authenticate each user with their personal password. Therefore authentication is disabled and each user simply accesses authorization profiles from a common Access Response stored in cache.

The same reasoning applies in cases where higher end security mechanisms such as Challenge Handshake Authentication Protocol (CHAP), Microsoft Challenge Handshake Authentication Protocol (MS-CHAP), or Extensible Authentication Protocol (EAP), which all use an encrypted password between the client and AAA offload server. To allow these unique, secure username and password profiles to retrieve their authorization profiles, authentication is bypassed.

To take advantage of this failover capability, you need to configure the authentication and authorization method list so that the cache server group is queried last when a user attempts to authenticate to the router. See the Method Lists in Authorization and Authentication Profile Caching section for more information.

A method list is a sequential list describing the authentication methods to be queried in order to authenticate a user. We support methods such as local (use the local Cisco IOS database), none (do nothing), RADIUS server group, or TACACS+ server group. Typically, more than one method can be configured into a method list. Cisco IOS software uses the first listed method to authenticate users. If that method fails to respond, the Cisco IOS software selects the next authentication method listed in the method list. This process continues until there is successful communication with a listed authentication method, or until all methods defined in the method list are exhausted.

To optimize network performance or provide failover capability using the profile caching feature you simply change the order of the authentication and authorization methods in the method list. To optimize network performance, make sure the cache server group appears first in the method list. For failover capability, the cache server group should appear last in the method list.

Because the number of usernames and profiles that can request to be authenticated or authorized at a given router on a given point of presence (POP) can be quite extensive, it would not be feasible to cache all of them. Therefore, only usernames and profiles that are commonly used or that share a common authentication and authorization response should be configured to use caching. Commonly used usernames such as aolip and aolnet, which are used for America Online (AOL) calls, or preauthentication dialed number identification service (DNIS) numbers used to connect Public Switched Telephone Network (PSTN) calls to a network attached storage device, along with domain-based service profiles, are all examples of usernames and profiles that can benefit from authentication and authorization caching.

To implement authorization and authentication profile caching, you would complete the following procedure:

1. Create cache profile groups and define the rules for what information is cached in each group.

Entries that match based on exact username, regular expressions, or specify that all authentication and authorization requests can be cached.

1. Update existing server groups to reference newly defined cache groups.
2. Update authentication or authorization method lists to use the cached information to optimize network performance or provide a failover mechanism.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    aaa new-model

4.    aaa cache profile group-name

5.    profile name [no-auth]

6.    Repeat Step 5 for each username you want to add to the profile group in Step 4.

7.    regexp matchexpression {any| only}[no-auth]

8.    Repeat Step 7 for each regular expression you want to add to the cache profile group defined in Step 4.

9.    all [no-auth]

10.    end

11.    show aaa cache group name

12.    clear aaa cache group name {profile name| all}

13.    debug aaa cache group

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	aaa new-model Example: Router(config)# aaa new-model	Enables the AAA access control model.
Step 4	aaa cache profile group-name Example: Router(config)# aaa cache profile networkusers@companyname	Defines an authentication and authorization cache profile server group and enters profile map configuration mode.
Step 5	profile name [no-auth] Example: Router(config-profile-map)# profile networkuser1 no-auth	Creates an individual authentication and authorization cache profile based on a username match. The name argument must be an exact match to a username being queried by an authentication or authorization service request. Use the no-auth keyword to bypass authentication for this user.
Step 6	Repeat Step 5 for each username you want to add to the profile group in Step 4.	--
Step 7	regexp matchexpression {any| only}[no-auth] Example: Router(config-profile-map)# regexp .*@example.com any no-auth	(Optional) Creates an entry in a cache profile group that matches based on a regular expression. If you use the any keyword, all unique usernames matching the regular expression are saved. If you use the only keyword, only one profile entry is cached for all usernames matching the regular expression. Use the no-auth keyword to bypass authentication for this user or set of users. Because the number of entries in a regular expression cache profile group could be in the thousands, and validating each request against a regular expression can be time consuming, we do not recommend using regular expression entries in cache profile groups.
Step 8	Repeat Step 7 for each regular expression you want to add to the cache profile group defined in Step 4.	--
Step 9	all [no-auth] Example: Router(config-profile-map)# all no-auth	(Optional) Specifies that all authentication and authorization requests are cached. Use the all command for specific service authorization requests, but it should be avoided when dealing with authentication requests.
Step 10	end Example: Router(config-profile-map)# end	Returns to privileged EXEC mode.
Step 11	show aaa cache group name Example: Router# show aaa cache group networkusers@companyname	(Optional) Displays all cache entries for a specified group.
Step 12	clear aaa cache group name {profile name| all} Example: Router# clear aaa cache group networkusers@companyname profile networkuser1	(Optional) Clears an individual entry or all entries in the cache.
Step 13	debug aaa cache group Example: Router# debug aaa cache group	(Optional) Displays debug information about cached entries.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    aaa new-model

4.    aaa group server radius group-name oraaa group server tacacs+ group-name

5.    cache authorization profile name

6.    cache authentication profile name

7.    cache expiry hours {enforce| failover}

8.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	aaa new-model Example: Router(config)# aaa new-model	Enables the AAA access control model.
Step 4	aaa group server radius group-name oraaa group server tacacs+ group-name Example: Router(config)# aaa group server radius networkusers@companyname	Enters RADIUS server group configuration mode. To enter TACACS+ server group configuration mode, use the aaa group server tacacs+ group-name command.
Step 5	cache authorization profile name Example: Router(config-sg-radius)# cache authorization profile networkusers@companyname	Activates the authorization caching rules in the profile networkusers for this RADIUS or TACACS+ server group. The name argument in this command is a AAA cache profile group name.
Step 6	cache authentication profile name Example: Router(config-sg-radius)# cache authentication profile networkusers@companyname	Activates the authentication caching rules in the profile networkusers for this RADIUS or TACACS+ server group.
Step 7	cache expiry hours {enforce| failover} Example: Router(config-sg-radius)# cache expiry 240 failover	(Optional) Sets the amount of time before a cache profile entry expires (becomes stale). Use the enforce keyword to specify that once a cache profile entry expires it is not used again. Use the failover keyword to specify that an expired cache profile entry can be used if all other methods to authenticate and authorize the user fail.
Step 8	end Example: Router(config-sg-radius)# end	Returns to privileged EXEC mode.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    aaa new-model

4.    aaa authorization {auth-proxy | cache | commands level | config-commands | configuration | console | exec | ipmobile | multicast | network | policy-if | prepaid | radius-proxy | reverse-access | subscriber-service | template} {default | list-name} [method1 [method2...]]

5.    aaa authentication ppp {default | list-name} method1 [method2...]

6.    aaa authentication login {default | list-name} method1 [method2...]

7.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	aaa new-model Example: Router(config)# aaa new-model	Enables the AAA access control model.
Step 4	aaa authorization {auth-proxy | cache | commands level | config-commands | configuration | console | exec | ipmobile | multicast | network | policy-if | prepaid | radius-proxy | reverse-access | subscriber-service | template} {default | list-name} [method1 [method2...]] Example: Router(config)# aaa authorization network default cache networkusers@companyname group networkusers@companyname	Enables AAA authorization and creates method lists, which define the authorization methods used when a user accesses a specified function.
Step 5	aaa authentication ppp {default | list-name} method1 [method2...] Example: Router(config)# aaa authentication ppp default cache networkusers@companyname group networkusers@companyname	Specifies one or more authentication methods for use on serial interfaces that are running PPP.
Step 6	aaa authentication login {default | list-name} method1 [method2...] Example: Router(config)# aaa authentication login default cache adminusers group adminusers	Sets the authentication at login.
Step 7	end Example: Router(config)# end	Returns to privileged EXEC mode.