Security Configuration Guide, Cisco IOS XE Amsterdam 17.3.x (Catalyst 9200 Switches) - Change of Authorization Support [Support] (2024)

Authentication provides a method to identify users, which includes the login and password dialog, challenge and response, messaging support, and encryption, depending on the selected security protocol. Authentication is the way a user is identified prior to being allowed access to the network and network services.

Change of Authorization Support

Cisco Identity Based Networking Services (IBNS) supports RADIUS change of authorization (CoA) commands for session query, reauthentication, and termination, port bounce and port shutdown, and service template activation and deactivation. This module provides information about the supported CoA commands for Cisco IBNS.

Information About CoA Support

RADIUS Change-of-Authorization Support

Cisco IOS software supports the RADIUS CoA extensions defined in RFC 5176 that are typically used in a push model to allow the dynamic reconfiguring of sessions from external AAA or policy servers. Per-session CoA requests are supported for session identification, session termination, host reauthentication, port shutdown, and port bounce. This model comprises one request (CoA-Request) and two possible response codes:

CoA acknowledgement (ACK) [CoA-ACK]
CoA nonacknowledgement (NAK) [CoA-NAK]

The request is initiated from a CoA client (typically a AAA or policy server) and directed to the device that acts as a listener.

The table below shows the RADIUS CoA commands and vendor-specific attributes (VSAs) supported by Cisco IBNS. All CoA commands must include the session identifier between the device and the CoA client.

Table 1. RADIUS CoA Commands Supported by Cisco IBNS
CoA Command	Cisco VSA
Activate service	Cisco:Avpair=“subscriber:command=activate-service” Cisco:Avpair=“subscriber:service-name=<service-name>” Cisco:Avpair=“subscriber:precedence=<precedence-number>” Cisco:Avpair=“subscriber:activation-mode=replace-all”
Deactivate service	Cisco:Avpair=“subscriber:command=deactivate-service” Cisco:Avpair=“subscriber:service-name=<service-name>”
Bounce host port	Cisco:Avpair=“subscriber:command=bounce-host-port”
Disable host port	Cisco:Avpair=“subscriber:command=disable-host-port”
Session query	Cisco:Avpair=“subscriber:command=session-query”
Session reauthenticate	Cisco:Avpair=“subscriber:command=reauthenticate” Cisco:Avpair=“subscriber:reauthenticate-type=last” or Cisco:Avpair=“subscriber:reauthenticate-type=rerun”
Session terminate	This is a standard disconnect request and does not require a VSA.
Interface template	Cisco:AVpair="interface-template-name=<interfacetemplate>"

Session Identification

For disconnect and CoA requests targeted at a particular session, the device locates the session based on one or more of the following attributes:

Acct-Session-Id (IETF attribute #44)
Audit-Session-Id (Cisco VSA)
Calling-Station-Id (IETF attribute #31, which contains the host MAC address)
IPv6 Attributes, which can be one of the following:
- Framed-IPv6-Prefix (IETF attribute #97) and Framed-Interface-Id (IETF attribute #96), which together create a full IPv6 address per RFC 3162
  See Also
  How to Create and Configure VLANs on a Cisco Switch with Example Basic Cisco Switch Configuration Example in 10 Steps Cisco IOS XR Setup and Upgrade Guide for Cisco 8000 Series Routers - Install Owner and Partner RPMs Using IOS XR Install Infrastructure [Cisco 8000 Series Routers][TUTO] Installer Homebrew Menu sur Switch 18.1.0 (et <) : Underground - Page 74 - Forums GAMERGEN.COM
- Framed-IPv6-Address
Plain IP Address (IETF attribute #8)

If more than one session identification attribute is included in the message, all of the attributes must match the session or the device returns a Disconnect-NAK or CoA-NAK with the error code Invalid Attribute Value.

For CoA requests targeted at a particular enforcement policy, the device returns a CoA-NAK with the error code Invalid Attribute Value if any of the above session identification attributes are included in the message.

CoA Activate Service Command

The CoA activate service command can be used to activate a service template on a session. The AAA server sends the request in a standard CoA-Request message using the following VSAs:

Cisco:Avpair=“subscriber:command=activate-service”

Cisco:Avpair=“subscriber:service-name=<service-name>”

Cisco:Avpair=“subscriber:precedence=<precedence-number>”

Cisco:Avpair=“subscriber:activation-mode=replace-all”

Because this command is session-oriented, it must be accompanied by one or more of the session identification attributes described in the Session Identification section. If the device cannot locate a session, it returns a CoA-NAK message with the Session Context Not Found error-code attribute. If the device locates a session, it initiates an activate template operation for the hosting port and a CoA-ACK is returned. If activating the template fails, a CoA-NAK message is returned with the Error-Code attribute set to the appropriate message.

If the device fails before returning a CoA-ACK to the client, the process is repeated on the new active device when the request is re-sent from the client. If the device fails after returning a CoA-ACK message to the client but before the operation is complete, the operation is restarted on the new active device.

CoA Deactivate Service Command

The CoA deactivate service command can be used to deactivate a service template on a session. The AAA server sends the request in a standard CoA-Request message using the following VSAs:

Cisco:Avpair=“subscriber:command=deactivate-service”

CoA Bounce Host Port Command

The CoA bounce host port command terminates a session and bounces the port (initiates a link down event followed by a link up event). The AAA server sends the request in a standard CoA-Request message with the following VSA:

Cisco:Avpair=“subscriber:command=bounce-host-port”

Because this command is session-oriented, it must be accompanied by one or more of the session identification attributes described in the Session Identification section. If the session cannot be located, the device returns a CoA-NAK message with the Session Context Not Found error-code attribute. If the session is located, the device disables the hosting port for a period of ten seconds, reenables it (port bounce), and returns a CoA-ACK.

The CoA bounce port command is useful as a last resort when an endpoint needs to acquire a new IP address after a change in authorization and this is the only way to indicate to the endpoint to restart the DHCP process. This can occur when there is a VLAN change and the endpoint is a device, such as a printer, that does not have a mechanism to detect a change on this authentication port. This command can cause a link flap on an authentication port, which triggers DHCP renegotiation from one or more hosts connected to this port.

CoA Disable Host Port Command

The CoA disable host port command administratively shuts down the authentication port that is hosting a session, which terminates the session. The AAA server sends the request in a standard CoA-Request message with the following VSA:

Cisco:Avpair=“subscriber:command=disable-host-port”

Because this command is session-oriented, it must be accompanied by one or more of the session identification attributes described in the Session Identification section. If the device cannot locate the session, it returns a CoA-NAK message with the Session Context Not Found error-code attribute. If the device locates the session, it disables the hosting port and returns a CoA-ACK message.

CoA Session Query Command

The CoA session query command requests service information about a subscriber session. The AAA server sends the request in a standard CoA-Request message containing the following VSA:

Cisco:Avpair=“subscriber:command=session-query”

Because this command is session-oriented, it must be accompanied by one or more of the session identification attributes described in the Session Identification section. If the device cannot locate a session, it returns a CoA-NAK message with the Session Context Not Found error-code attribute. If the device locates a session, it performs a session query operation on the session and returns a CoA-ACK message.

CoA Session Reauthenticate Command

To initiate session authentication, the AAA server sends a standard CoA-Request message containing the following VSAs:

Cisco:Avpair=“subscriber:command=reauthenticate”

Cisco:Avpair=“subscriber:reauthenticate-type=<last | rerun>”

“reauthenticate-type” defines whether the CoA reauthentication request uses the authentication method that last succeeded on the session or whether the authentication process is completely rerun.

The following rules apply:

“subscriber:command=reauthenticate” must be present to trigger a reauthentication.
If “subscriber:reauthenticate-type” is not specified, the default behavior is to rerun the last successful authentication method for the session. If the method reauthenticates successfully, all old authorization data is replaced with the new reauthenticated authorization data.
“subscriber:reauthenticate-type” is valid only when included with “subscriber:command=reauthenticate.” If it is included in another CoA command, the VSA will be silently ignored.

If the device fails before returning a CoA-ACK to the client, the process is repeated on the new active device when the request is resent from the client. If the device fails after returning a CoA-ACK message to the client but before the operation is complete, the operation is restarted on the new active device.

CoA Session Terminate Command

A CoA Disconnect-Request command terminates a session without disabling the host port. This command causes reinitialization of the authenticator state machine for the specified host, but does not restrict the host’s access to the network. If the session cannot be located, the device returns a Disconnect-NAK message with the Session Context Not Found error-code attribute. If the session is located, the device terminates the session. After the session has been completely removed, the device returns a Disconnect-ACK.

If the device fails before returning a CoA-ACK to the client, the process is repeated on the new active device when the request is re-sent from the client.

To restrict a host’s access to the network, use a CoA Request with the Cisco:Avpair=“subscriber:command=disable-host-port” VSA. This command is useful when a host is known to cause problems on the network and network access needs to be immediately blocked for the host. When you want to restore network access on the port, reenable it using a non-RADIUS mechanism.

Feature Information for CoA Support

Table 2. Feature Information for CoA Support
Release	Feature Name	Feature Information
Cisco IOS XE Fuji 16.9.2	Change of Authorization	Supports CoA requests for initiating the following: Activating and deactivating service templates on sessions Port bounce Port shutdown Querying a session Reauthenticating a session Terminating a session These VSAs are sent in a standard CoA-Request message from a AAA server.