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This feature enhances the authentication, authorization, and accounting (AAA) capability to meet high availability (HA) criteria for locally terminated Point-to-Point Protocol (PPP) over Ethernet (PPPoE) and PPPoEoX sessions, where X represents VLAN or QinQ. The following Feature Manager features are supported in this implementation of AAA HA:
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
If an administrator changes the protocol of a server group (for example, from RADIUS to TACACS+), HA will not be available for sessions configured to use that server group.
IP sessions are not supported in this implementation of AAA HA.
Cisco HA delivers carrier grade reliability with Cisco devices running Cisco IOS XE software. Carrier grade means that service disruption because of outages, service upgrades, or other maintenance activities on Cisco IOS XE platforms are rarely experienced. To achieve this level of service, Cisco uses two route processors to manage and control the sessions and services for each device. One processor is active and the other is in standby mode, ready to provide backup. A transition from the active processor to the standby processor is transparent to the end user, but not necessarily to the service provider.
The router must maintain the following information during transient component failures:
Authentication status of clients
Authorization status
Accounting and billing information
To maintain this information during transitions to the standby processor, Cisco IOS XE software uses an HA replay model to re-create as much state and database information as possible between the active and standby devices. The HA replay model works within existing external AAA server protocols to achieve the desired behavior.
For authentication, only the following state information is maintained: knowledge that a session authenticated on the active processor need not be reauthenticated on the standby processor. Each authentication protocol, such as local, TACACS+, or RADIUS, responds in its protocol-specific way to an authentication request from a standby device. All AAA client authentication replies on a standby device should be successful.
The HA process for authorization data is different from the authentication process. The AAA server caches the authorization responses for the sessions in order to provide the appropriate authorization attributes to AAA clients during a session replay. AAA clients use the authorization attributes to create a session copy on the standby route processor.
The AAA HA accounting framework takes advantage of existing AAA features such as system accounting and periodic accounting to limit the loss of accounting and billing information caused by a switchover between an active processor and a standby processor.
System accounting is a separate accounting capability that informs AAA servers about the state of a client device, such as a router. The AAA server receives a “System-Off” message when a controlled restart takes place on a client device. The message notifies the AAA server to clear any active sessions being managed for the specified client. When the client restarts and becomes available for new sessions, the AAA server receives a “System-On” message. The “System-On” message is also sent following uncontrolled restarts caused by device failures or other events that do not generate a “System-Off” message. In either case, the AAA server no longer maintains any active sessions for the specified client device. The server bills or accounts for the sessions prior to the “System-On” message and starts a new session.
AAA’s accounting HA solution does not add any new requirements to system accounting for AAA servers. Any switchover will look like a very fast, minimally disruptive outage. Although end users do not experience any loss of service during an HA switchover, AAA servers reset their sessions and restart accounting for all switched-over sessions.
You can use periodic accounting to dynamically update records of session utilization for billing purposes. Periodic accounting minimizes the loss of usage statistics. HA does not eliminate the need to configure periodic accounting on a device if you require dynamic usage statistics for billing purposes. To achieve the HA level of reliability, the existing network topology configuration must be maintained.
There are no configuration tasks associated with this feature. If you maintain your network topology for HA, then the AAA functions automatically participate in the HA feature for locally terminated PPPoX sessions.
1.
enable
2.
debug
aaa
redundancy
3.
disable
Command or Action | Purpose | |
---|---|---|
Step 1 |
enable
Example: Router> enable |
Enters the privileged EXEC mode.
|
Step 2 |
debug
aaa
redundancy
Example: Router# debug aaa redundancy |
Displays AAA synchronization data for the session synchronization to the standby device. |
Step 3 |
disable
Example: Router# disable |
Exits to user EXEC mode. |
Related Topic |
Document Title |
---|---|
Cisco IOS commands |
|
Cisco debug commands |
Cisco IOS Debug Command Reference |
Cisco IOS High Availability commands |
Cisco IOS High Availability Command Reference |
BGP support for NSF |
BGP Support for Nonstop Routing (NSR) with Stateful Switchover (SSO) module in the Cisco IOS IP Routing: BGP Configuration Guide |
EIGRP NSF awareness |
EIGRP Nonstop Awareness module in the Cisco IOS IP Routing: EIGRP Configuration Guide |
IPv6 BGP graceful restart |
Implementing Multiprotocol BGP for IPv6 module in the Cisco IOS IPv6 Configuration Guide |
IPv6 RIP |
Implementing RIP for IPv6 module in the Cisco IOS IPv6 Configuration Guide |
IPv6 static routes |
Implementing Static Routes for IPv6 module in the Cisco IOS IPv6 Configuration Guide |
NSF/SSO--802.3ah OAM Support |
Using Ethernet Operations, Administration, and Maintenance module in the Cisco IOS Carrier Ethernet Configuration Guide |
NSF/SSO--Any Transport over MPLS (AToM) |
Any Transport over MPLS and AToM Graceful Restart module in the Cisco IOS Multiprotocol Label Switching Configuration Guide |
NSF/SSO--E-LMI Support |
Configuring Ethernet Local Management Interface at a Provider Edge module in the Cisco IOS Carrier Ethernet Configuration Guide |
NSF/SSO--MPLS VPN |
Configuring NSF/SSO--MPLS VPN module in the MPLS Configuration Guide |
Virtual Private LAN Services |
NSF/SSO/ISSU Support for VPLS module in the Cisco IOS Multiprotocol Label Switching Configuration Guide |
Standard |
Title |
---|---|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
-- |
MIB |
MIBs Link |
---|---|
No new or modified MIBs are supported, and support for existing MIBs has not been modified. |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFC |
Title |
---|---|
RFC 3623 |
Graceful OSPF Restart |
RFC 3847 |
Restart Signaling for Intermediate System to Intermediate System (IS-IS) |
RFC 4781 |
Graceful Restart Mechanism for BGP |
Description |
Link |
---|---|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
---|---|---|
AAA High Availability Support for Local PPPoX Sessions |
Cisco IOS XE Release 2.1 |
This feature enhances the AAA capability to meet HA criteria for locally terminated PPPoE and PPPoEoX sessions. The following command was introduced or modified: debug aaa redundancy. |