Configuring Stateful Switchover

• For hardware-redundant platforms, two Route Processors (RPs) must be installed in the chassis, each running the same version or a compatible version of the Cisco software.
• Before copying a file to flash memory, be sure that ample space is available in flash memory. Compare the size of the file you are copying to the amount of available flash memory shown. If the space available is less than the space required by the file you will copy, the copy process will not continue and an error message similar to the following will be displayed:

%Error copying tftp://image@server/tftpboot/filelocation/imagename (Not enough space on device). 
 

• Distributed Cisco Express Forwarding must be enabled on any networking device configured to run SSO.
• For Nonstop Forwarding (NSF) support, neighbor routers must be running NSF-enabled images, though SSO need not be configured on the neighbor device.

• On Cisco 10000 series devices only, to boot both Performance Routing Engines (PREs) from the TFTP boot server, you must use the ip address negotiated command in interface configuration mode to enable DHCP on the PRE. Otherwise, you will get a duplicate IP address error because of the synchronization of the IP address from the active to the standby Route Processor (RP).

• On the Cisco 7507 and Cisco 7513 routers, any combination of RSP8 and RSP16 devices, or any combination of RSP2 and RSP4, are required.

• Both RPs must run the same Cisco software image. If the RPs are operating different Cisco software images, the system reverts to RPR mode even if SSO is configured.
• Configuration changes made through SNMP may not be automatically configured on the standby RP after a switchover occurs.
• Load sharing between dual processors is not supported.
• The Hot Standby Routing Protocol (HSRP) is not supported with Cisco Nonstop Forwarding with Stateful Switchover. Do not use HSRP with Cisco Nonstop Forwarding with Stateful Switchover.
• Enhanced Object Tracking (EOT) is not stateful switchover-aware and cannot be used with HSRP, Virtual Router Redundancy Protocol (VRRP), or Gateway Load Balancing Protocol (GLBP) in SSO mode.
• Multicast is not SSO-aware and restarts after switchover; therefore, multicast tables and data structures are cleared upon switchover.

• The configuration registers on both RPs must be set the same for the networking device to behave the same when either RP is rebooted.
• During the startup (bulk) synchronization, configuration changes are not allowed. Before making any configuration changes, wait for a message similar to the following:

%HA-5-MODE:Operating mode is sso, configured mode is sso.

• On the Cisco 7304 router, a message similar to the following appears (the actual slot number depends on which slot has the active processor):

%HA-6-STANDBY_READY: Standby RP in slot n
 is operational in SSO mode

• If the router is configured for SSO mode, and the active RP fails before the standby is ready to switch over, the router will recover through a full system reset.

• Label-controlled ATM (LC-ATM) functionality does not co-exist with SSO in this release.
• The ATM line protocol does not support stateful switchover capability for the following features in this release:
  • SVCs
  • Switched virtual paths (SVPs)
  • Tagged virtual circuits (TVCs)
  • Point-to-multipoint SVC
  • Integrated Local Management Interface (ILMI)
  • Signaling and Service Specific Connection Oriented Protocol (SSCOP)
  • ATM Connection Manager, permanent virtual circuit (PVC) discovery, ATM applications
  • Backward or version compatibility
  • Statistics and accounting
  • Zero ATM cell loss

• The following Frame Relay features are not synchronized between the active and standby RPs in this release: Frame Relay statistics; enhanced LMI (ELMI); Link Access Procedure, Frame Relay (LAPF); SVCs; and subinterface line state.

Note	The subinterface line state is determined by the PVC state, which follows the line card protocol state on DCE interfaces, and is learned from first LMI status exchange after switchover on DTE interfaces.

• Frame Relay SSO is supported with the following features:
  • Serial interfaces
  • DTE and DCE LMI (or no keepalives)
  • PVCs (terminated and switched)
  • IP
• When no LMI type is explicitly configured on a DTE interface, the autosensed LMI type is synchronized.
• LMI sequence numbers are not synchronized between the active and standby RPs by default.

LMI keepalive messages contain sequence numbers so that each side (network and peer) of a PVC can detect errors. An incorrect sequence number counts as one error. By default, the switch declares the line protocol and all PVCs down after three consecutive errors. Although it seems that synchronizing LMI sequence numbers might prevent dropped PVCs, the use of resources required to synchronize LMI sequence numbers for potentially thousands of interfaces (channelized) on larger networking devices might be a problem in itself. The networking device can be configured to synchronize LMI sequence numbers. Synchronization of sequence numbers is not necessary for DCE interfaces.

• Changes to the line protocol state are synchronized between the active and standby RPs. The line protocol is assumed to be up on switchover, providing that the interface is up.
• PVC state changes are not synchronized between the active and standby RPs. The PVC is set to the up state on switchover provided that the line protocol state is up. The true state is determined when the first full status message is received from the switch on DTE interfaces.
• Subinterface line state is not synchronized between the active and standby RPs. Subinterface line state is controlled by the PVC state, by configuration settings, or by the hardware interface state when the PVC is up. On switchover, the subinterface state is set to up, providing that the subinterfaces are not shut down and the main interface is up and the line protocol state is up. On DTE devices, the correct state is learned after the first LMI status exchange.
• Dynamic maps are not synchronized between the active and standby RPs. Adjacency changes as a result of dynamic map change are relearned after switchover.
• Dynamically learned PVCs are synchronized between the active and standby RPs and are relearned after the first LMI status exchange.
• For Multilink Frame Relay bundle links, the state of the local bundle link and peer bundle ID is synchronized.
• For a Multilink Frame Relay bundle, the peer ID is synchronized.

• The following PPP features are not supported in this release: dialer; authentication, authorization, and accounting (AAA), IPPOOL, Layer 2 (L2X), Point-to-Point Tunneling Protocol (PPTP), Microsoft Point-to-point Encryption (MPPE), Link Quality Monitoring (LQM), link or header compression, bridging, asynchronous PPP, and XXCP.
• We recommend that the keepalive value be set to 20 seconds on Cisco 7500 series routers for each peer in a PPP connection.

• On Cisco 12000 series devices with three or more RPs in a chassis, after negotiation of active and standby RP, the non-active (remaining) RPs do not participate in router operation.
• On the Cisco 12000 and 7500 series routers, if any changes to the fabric configuration happen simultaneously with an RP switchover, the chassis is reset and all line cards are reset.
• On the Cisco 12000 series and 10000 series Internet routers, if a switchover occurs before the bulk synchronization step is complete, the new active RP may be in inconsistent states. The router will be reloaded in this case.
• SSO does not support TFTP boot operation on the Cisco 12000 series Internet routers. The software images must be downloaded to the flash memory cards on the router.
• Any line cards that are not online at the time of a switchover (line cards not in Cisco software running state) are reset and reloaded on a switchover.
• The following line cards support SSO and Cisco NSF:
  • All Engine-0, Engine-2, and Engine-4 Packet over SONET (PoS) line cards
  • All Engine-0 ATM line cards
  • All nonchannelized DS3 and E3 line cards
  • All Engine-0 channelized line cards
  • 1XGE and 3XGE line cards
• The following Engine-0 line cards are supported:
  • 4-port OC-3 PoS
  • 1-port OC-12 PoS
  • 1-port O-12 ATM
  • 4-port OC-3 ATM
  • 6-port DS3
  • 12-port DS3
  • 6-port E3
  • 12-port E3
  • 6-port CT3
  • 1-port CHOC-12->DS3
  • 6-port CT3->DS1
  • 1-port CHOC-12/STM4->OC-3/STM1 POS
  • 2-port CHOC-3/STM-1->DS1/E1
• The following Engine-1 line cards are supported:
  • 2-Port OC-12/STM-4c DPT
• The following Engine-2 line cards are supported:
  • 1-port OC-48 POS
  • 1-port OC-48/STM-16c DPT
  • 4-port OC-12 POS
  • 8-port OC-3 POS
  • 8-port OC-3/STM-1c ATM
  • 16-port OC-3 POS
• The following Engine-4 line cards are supported:
  • 1-port OC-192 POS
  • 4-port OC-48 POS
• The following IP Service Engine (ISE) line cards are supported:
  • 4-port OC-3c/STM-1c POS/SDH ISE
  • 8-port OC-3c/STM-1c POS/SDH ISE
  • 16-port OC-3c/STM-1c POS/SDH ISE
  • 4-port OC-12c/STM-4c POS/SDH ISE
  • 1-port OC-48c/STM-16c POS/SDH ISE
  • 4-port channelized OC-12/STM-4 (DS3/E3, OC-3c/STM-1c) POS/SDH ISE
  • 1-port channelized OC-48/STM-16 (DS3/E3, OC-3c/STM-1c) POS/SDH ISE
  • 4-port OC-12c/STM-4c DPT ISE

• When configuring boot variables, booting from the TFTP boot server is not supported except on Cisco 10000 series Internet routers only.
• Both RPs must run the same Cisco software image. If the RPs are operating different Cisco software images, the system reverts to RPR mode even if SSO is configured. On the Cisco 10000 series Internet router, the system reverts to RPR+ mode.
• If a switchover occurs before the bulk synchronization step is complete, the new active RP may be in an inconsistent state. The router will be reloaded in this case.
• SSO supports TFTP boot operation on the Cisco 10000 series Internet routers.
• The following line cards support SSO and Cisco NSF:
  • 6-port Universal (Channelized or Clear-channel) DS3
  • 8-port E3/DS3
  • 1-port OC-12 POS
  • 6-port OC-3 POS
  • 1-port Gigabit Ethernet
  • 1-port Channelized OC-12
  • 4-port Channelized STM1
  • 24-port channelized E1/T1
  • 1-port OC-12 ATM
  • 4-port OC-3 ATM

• On the Cisco 7500 series routers, if any changes to the fabric configuration happen simultaneously with an RP switchover, the chassis is reset and all line cards are reset.
• On Cisco 7500 series routers configured for SSO mode, during synchronization between the active and standby RPs, the configured mode will be RPR. After the synchronization is complete, the operating mode will be SSO. If a switchover occurs before the synchronization is complete, the switchover will be in RPR mode.
• On Cisco 7500 series routers, legacy IPs will default to RPR mode and must be reloaded. If three or more legacy IPs are present, then all the line cards, including the VIPs, must be reloaded.
• SSO does not support TFTP boot operation on the Cisco 7500 series Internet routers. The software images must be downloaded to the flash memory cards on the router.
• SSO operates only on a Cisco 7500 series Internet router that has VIPs as the port adapters. Systems with legacy interface processors not compatible with RPR+ or SSO mode will always get reset and reloaded upon switchover.
• To support SSO, a router must have either a combination of two RSP8 and RSP16 devices or a combination of RSP2 and RSP4 devices. A combination of RSP8 or RSP16 with RSP2 or RSP4 devices on a platform is not supported. Only the Cisco 7507 and Cisco 7513 support dual processors, which is required to support SSO.
• Simultaneous changes to the configuration from multiple CLI sessions is not allowed. Only one configuration session is allowed to enter into configuration mode at a time, other sessions will not be able to enter into configuration mode.
• Using “send break” to break or pause the system is not recommended and may cause unpredictable results. To initiate a manual switchover, use the redundancy force-switchover command.
• The following line cards support SSO and Cisco NSF:
  • PA-MC-E3, 1-port multichannel E3 port adapter (PA)
  • PA-MC-T3, 1-port multichannel T3 PA
  • PA-MC-2E1/120, 2-port multichannel E1 PA with G.703 120-ohm interface
  • PA-MC-2TE1, 2-port multichannel T1 PA with integrated channel service unit (CSU) and data service unit (DSU) devices
  • PA-MC-2T3+, 2-port multichannel T3 PA
  • PA-MC-4T, 4-port multichannel T1 PA with integrated CSU and DSU devices
  • PA-MC-8T1, 8-port multichannel T1 PA with integrated CSU and DSU devices
  • PA-MC-8DSX1, 8-port multichannel DS1 PA with integrated DSUs
  • PA-MC-8E1/120, 8-port multichannel E1 PA with G.703 120-ohm interface
  • PA-4T+, 4-port serial PA enhanced
  • PA-8T-V35, 8-port serial V.35 PA
  • PA-8T-232, 8-port serial 232 PA
  • PA-8T-X21, 8-port serial X.21 PA
  • PA-E3, 1-port E3 serial PA with E3 DSU
  • PA-T3+, 1-port T3 serial PA enhanced
  • PA-2E3, 2-port E3 serial PA with E3 DSUs
  • PA-2T3+, 2-port T3 serial PA enhanced
  • PA-H, 1-port High-Speed Serial Interface (HSSI) PA
  • PA-2H, 2-port HSSI PA
  • PA-2FE-TX, 2-port Ethernet 100BASE-TX PA
  • PA-2FE-FX, 2-port Ethernet 100BASE-FX PA
  • PA-FE-TX, 1-port Fast Ethernet 100BASE-TX PA
  • PA-FE-FX, 1-port Fast Ethernet 100BASE-FX PA
  • PA-4E 4-port, Ethernet 10BASE-T PA
  • PA-8E 8-port, Ethernet 10BASE-T PA
  • PA-A3-E3, 1-port ATM enhanced E3 PA
  • PA-A3-T3, 1-port ATM enhanced DS3 PA
  • PA-A3-OC3MM, 1-port ATM enhanced OC-3c/STM-1 multimode PA
  • PA-A3-OC3SMI, 1-port ATM enhanced OC-3c/STM-1 single-mode (IR) PA
  • PA-A3-OC3SML, 1-port ATM enhanced OC-3c/STM-1 single-model (LR) PA
  • PA-POS-OC3MM, 1-port PoS OC-3c/STM-1 multimode PA
  • PA-POS-OC3SMI, 1-port PoS OC-3c/STM-1 single-mode (IR) PA
  • PA-POS-OC3SML, 1-port PoS OC-3c/STM-1 single-mode (LR) PA
  • PA-A3-8E1IMA, 8-port ATM inverse multiplexer E1 (120-ohm) PA
  • PA-A3-8T1IMA, 8-port ATM inverse multiplexer T1 PA
  • PA-4E1G/75, 4-port E1 G.703 serial PA (75-ohm/unbalanced)
  • PA-4E1G/120, 4-port E1 G.703 serial PA (120-ohm/balanced)
  • PA-MCX-8TE1
  • PA-MCX-4TE1
  • PA-MCX-2TE1
  • All VIP2 and VIP4 line cards
  • PA/VIP Combinations: Gigabit-Ethernet IP (GEIP) and GEIP+

• Switchovers in SSO mode will not cause the reset of any line cards.
• Interfaces on the RP itself are not stateful and will experience a reset across switchovers. The GE interfaces on the RPs are reset across switchovers and do not support SSO.
• SSO does not support TFTP boot operation on Cisco 7304 series routers. The software images must be downloaded to the flash memory cards on the router.
• On the Cisco 7304 routers, the two RPs must be the same type, either both NSE-100 or both NPE-G100. Mixing the two types is not supported.
• The presence of the PCI port adapter carrier card will force the system to fall back to the RPR redundancy mode.
• In Cisco IOS releases 12.2(20)S to 12.2(20)S2, the presence of the PA carrier card (7300-CC-PA) or the SPA carrier card (MSC-100) forces the system to RPR mode.
• In Cisco IOS Release 12.2(20)S3, both the PA carrier card and SPA carrier card support SSO mode. The PA carrier card does not support RPR+ mode.
• In Cisco IOS Release 12.2(20)S4 and later releases, all line cards support RPR+ and SSO modes.

• Only RPR and SSO are supported on Cisco ASR 1000 Aggregation Services routers.
• RPR and SSO can be used on Cisco ASR 1000 Aggregation Services routers to enable a second Cisco software process on a single RP. This configuration option is only available on Cisco ASR 1002 and Cisco ASR 1004 routers. On all other Cisco ASR 1000 Aggregation Services routers, the second Cisco software process can run on the standby RP only.
• A second Cisco software process can only be enabled using RPR or SSO if the RP is using 4 GB of DRAM. The show version command output shows the amount of DRAM configured on the router.
• Enabling software redundancy on the Cisco ASR 1001, 1002, and 1004 routers can reduce the Cisco IOS memory by more than half and adversely affect control plane scalability. We recommend that you use hardware redundant platforms, such as the Cisco ASR 1006 or 1013 routers, in networks where both scalability and high availability are critical.

SSO provides protection for network edge devices with dual RPs that represent a single point of failure in the network design, and where an outage might result in loss of service for customers.

In Cisco networking devices that support dual RPs, SSO takes advantage of RP redundancy to increase network availability. The feature establishes one of the RPs as the active processor while the other RP is designated as the standby processor, and then synchronizing critical state information between them. Following an initial synchronization between the two processors, SSO dynamically maintains RP state information between them.

On Cisco ASR 1000 series routers, SSO can also be used to enable a second Cisco software process on the same RP. This second Cisco IOS process acts as a standby process for the active Cisco software process, and also allows certain subpackages to be upgraded without experiencing any router downtime.

A switchover from the active to the standby processor occurs when the active RP fails, is removed from the networking device, or is manually taken down for maintenance.

SSO is used with the Cisco Nonstop Forwarding (NSF) feature. Cisco NSF allows for the forwarding of data packets to continue along known routes while the routing protocol information is being restored following a switchover. With Cisco NSF, peer networking devices do not experience routing flaps, thereby reducing loss of service outages for customers.

The figure below illustrates how SSO is typically deployed in service provider networks. In this example, Cisco NSF with SSO is primarily at the access layer (edge) of the service provider network. A fault at this point could result in loss of service for enterprise customers requiring access to the service provider network.

For Cisco NSF protocols that require neighboring devices to participate in Cisco NSF, Cisco NSF-aware software images must be installed on those neighboring distribution layer devices. Additional network availability benefits might be achieved by applying Cisco NSF and SSO features at the core layer of your network; however, consult your network design engineers to evaluate your specific site requirements.

Additional levels of availability may be gained by deploying Cisco NSF with SSO at other points in the network where a single point of failure exists. The figure below illustrates an optional deployment strategy that applies Cisco NSF with SSO at the enterprise network access layer. In this example, each access point in the enterprise network represents another single point of failure in the network design. In the event of a switchover or a planned software upgrade, enterprise customer sessions would continue uninterrupted through the network.

• High System Availability
  
• Route Processor Redundancy Mode
  
• Route Processor Redundancy Plus
  
• Stateful Switchover Mode
  
• Redundancy Modes by Platform and Software Release
  

In networking devices running SSO, both RPs must be running the same configuration so that the standby RP is always ready to assume control if the active RP fails.

To achieve the benefits of SSO, synchronize the configuration information from the active RP to the standby RP at startup and whenever changes to the active RP configuration occur. This synchronization occurs in two separate phases:

• While the standby RP is booting, the configuration information is synchronized in bulk from the active RP to the standby RP.
• When configuration or state changes occur, an incremental synchronization is conducted from the active RP to the standby RP.

• Bulk Synchronization During Initialization
  
• Incremental Synchronization
  

• Switchover Conditions
  
• Switchover Time
  
• Online Removal of the Active RP
  
• Fast Software Upgrade
  
• Core Dump Operation
  

The virtual template manager feature for SSO provides virtual access interfaces for sessions that are not HA-capable and are not synchronized to the standby router. The virtual template manager uses a redundancy facility (RF) client to allow the synchronization of the virtual interfaces in real time as they are created.

The virtual databases have instances of distributed FIB entries on line cards. Line cards require synchronization of content and timing in all interfaces to the standby processor to avoid incorrect forwarding. If the virtual access interface is not created on the standby processor, the interface indexes will be corrupted on the standby router and line cards, which will cause problems with forwarding.

SSO-supported line protocols and applications must be SSO-aware. A feature or protocol is SSO-aware if it maintains, either partially or completely, undisturbed operation through an RP switchover. State information for SSO-aware protocols and applications is synchronized from active to standby to achieve stateful switchover for those protocols and applications.

The dynamically created state of SSO-unaware protocols and applications is lost on switchover and must be reinitialized and restarted on switchover.

SSO-aware applications are either platform-independent, such as in the case of line protocols or platform-dependent (such as line card drivers). Enhancements to the routing protocols (Cisco Express Forwarding, Open Shortest Path First, and Border Gateway Protocol [BGP]) have been made in the SSO feature to prevent loss of peer adjacency through a switchover; these enhancements are platform-independent.

• Line Protocols
  
• Quality of Service
  
• IPv6 Support for Stateful Switchover
  
• Line Card Drivers
  
• APS
  
• Routing Protocols and Nonstop Forwarding
  
• Network Management
  
• SSO for Circuit Emulation Services
  

SUMMARY STEPS

1.    enable

2.    copy tftp {slot | disk}device-number : filename

3.    copy tftp {slave | stby-}{slot | disk}device-number : filename

4.    exit

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	copy tftp {slot | disk}device-number : filename Example: Router# copy tftp slot0:image1	Copies a Cisco software image onto the flash device of the active RP.
Step 3	copy tftp {slave | stby-}{slot | disk}device-number : filename Example: Router# copy tftp stby-slot0:image1	Copies a Cisco software image onto the flash device of the standby RP.
Step 4	exit Example: Router# exit	Exits to user EXEC mode.

SUMMARY STEPS

1.    enable

2.    show version

3.    configure terminal

4.    no boot system {flash [flash-fs:][partition-number:][filename ] | ftpfilename [ip-address ]}

5.    boot system {flash [flash-fs:][partition-number:][filename ] | tftpfilename [ip-address ]}

6.    config-register value

7.    exit

8.    copy running-config startup-config

9.    reload

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	show version Example: Router# show version	Obtains the current configuration register setting.
Step 3	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 4	no boot system {flash [flash-fs:][partition-number:][filename ] | ftpfilename [ip-address ]} Example: Router(config)# no boot system flash	(Optional) Clears any existing system flash or TFTP boot image specification.
Step 5	boot system {flash [flash-fs:][partition-number:][filename ] | tftpfilename [ip-address ]} Example: Example: Router(config)# boot system flash	Specifies the filename of stored image in flash memory or, for Cisco 10000, on a TFTP server.
Step 6	config-register value Example: Router(config)# config-register 0x2102	Modifies the existing configuration register setting to reflect the way in which you want to load a system image.
Step 7	exit Example: Router(config)# exit	Exits global configuration mode and returns the router to privileged EXEC mode.
Step 8	copy running-config startup-config Example: Router# copy running-config startup-config	Saves the configuration changes to the startup configuration file.
Step 9	reload Example: Router# reload	Reboots both RPs on the device to ensure that changes to the configuration take effect.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    hw-module slot slot-number image file-spec

4.    redundancy

5.    mode sso

6.    end

7.    copy running-config startup-config

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	hw-module slot slot-number image file-spec Example: Router(config)# hw-module slot 6 image slot0:rsp-pv-mz	(Optional) For Cisco 7500 series devices only. Specifies the image to be used by an RP at initialization. Repeat this step for both the active and standby RPs.
Step 4	redundancy Example: Router(config)# redundancy	Enters redundancy configuration mode.
Step 5	mode sso Example: Router(config)# mode sso	Sets the redundancy configuration mode to SSO on both the active and standby RP. Note    After configuring SSO mode, the standby RP will automatically reset.
Step 6	end Example: Router(config-red)# end	Exits redundancy configuration mode and returns the router to privileged EXEC mode.
Step 7	copy running-config startup-config Example: Router# copy running-config startup-config	Saves the configuration changes to the startup configuration file.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    frame-relay redundancy auto-sync lmi-sequence-numbers

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	frame-relay redundancy auto-sync lmi-sequence-numbers Example: Router(config)# frame-relay redundancy auto-sync lmi-sequence-numbers	Configures automatic synchronization of Frame Relay LMI sequence numbers between the active RP and the standby RP.

SUMMARY STEPS

1.    enable

2.    show redundancy [clients | counters | history | switchover history | states]

3.    show redundancy states

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	show redundancy [clients | counters | history | switchover history | states] Example: Router# show redundancy	Displays SSO configuration information.
Step 3	show redundancy states Example: Router# show redundancy states	Verifies that the device is running in SSO mode.

SUMMARY STEPS

1.    enable

2.    copy tftp {slot | disk}device-number:filename

3.    copy tftp {slave | stby-}{slot | disk } device-number : filename

4.    configure terminal

5.    no hw-module slot slot-number image file-spec

6.    hw-module slot slot-number image file-spec

7.    no boot system flash [flash-fs:][partition-number:][filename ]

8.    boot system flash [flash-fs:][partition-number:][filename ]

9.    config-register value

10.    exit

11.    copy running-config startup-config

12.    hw-module standby-cpu reset

13.    reload standby-cpu

14.    redundancy force-switchover [main-cpu]

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	copy tftp {slot | disk}device-number:filename Example: Router# copy tftp slot0:image1	Copies a Cisco software image onto the flash device of the active RP.
Step 3	copy tftp {slave | stby-}{slot | disk } device-number : filename Example: Router# copy tftp stby-slot0:image1 Example:	Copies a Cisco software image onto the flash device of the standby RP.
Step 4	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 5	no hw-module slot slot-number image file-spec Example: Router(config)# no hw-module slot 6 image slot0:rsp-pv-mz	For Cisco 7500 series routers only. Clears existing configuration entries for the specified image on an RSP. Configuration entries are additive, and the networking device will use the first image found in the configuration file. Repeat this step for both the active and standby RSPs.
Step 6	hw-module slot slot-number image file-spec Example: Router(config)# hw-module slot 6 image slot0:image1	For Cisco 7500 series routers only. Specifies the image to be used by the RSP at initialization. Configuration entries are additive, and the networking device will use the first image found in the configuration file. Repeat this step for both the active and standby RSPs.
Step 7	no boot system flash [flash-fs:][partition-number:][filename ] Example: Router(config)# no boot system flash	Clears the current boot image filename from the configuration file.
Step 8	boot system flash [flash-fs:][partition-number:][filename ] Example: Router(config)# boot system flash	Specifies the filename of a boot image stored in flash memory.
Step 9	config-register value Example: Router(config)# config-register 0x2102	Modifies the existing configuration register setting to reflect the way in which you want to load a system image.
Step 10	exit Example: Router(config)# exit	Exits global configuration mode and returns the router to privileged EXEC mode.
Step 11	copy running-config startup-config Example: Router# copy running-config startup-config	Saves the configuration changes to your startup configuration in NVRAM so that the router will boot with the configuration you have entered.
Step 12	hw-module standby-cpu reset Example: Router# hw-module standby-cpu reset	Resets and reloads the standby processor with the specified Cisco software image, and executes the image.
Step 13	reload standby-cpu Example: Router# reload standby-cpu	(Optional) For Cisco 12000 series Internet routers only. Resets and reloads the standby processor with the specified Cisco software image, and executes the image.
Step 14	redundancy force-switchover [main-cpu] Example: Router# redundancy force-switchover	Forces a switchover to the standby RP. For Cisco 10000 series Internet routers: The main-cpu keyword is required.

• The standby RP was reset, but there are no messages describing what happened--To display a log of SSO events and clues as to why a switchover or other event occurred, enter the show redundancy history command on the newly active RP.
• The show redundancy states command shows an operating mode that is different than what is configured on the networking device--On certain platforms the output of the show redundancy states command displays the actual operating redundancy mode running on the device, and not the configured mode as set by the platform. The operating mode of the system can change depending on system events. For example, SSO requires that both RPs on the networking device be running the same software image; if the images are different, the device will not operate in SSO mode, regardless of its configuration.
• Reloading the device disrupts SSO operation--The SSO feature introduces a number of commands, including commands to manually cause a switchover. The reload command is not an SSO command. This command causes a full reload of the box, removing all table entries, resetting all line cards, and thereby interrupting network traffic forwarding. To avoid reloading the box unintentionally, use the redundancy force-switchover command.
• During a software upgrade, the networking device appears to be in a mode other than SSO--During the software upgrade process, the show redundancy command indicates that the device is running in a mode other than SSO.

  This is normal behavior. Until the FSU procedure is complete, each RP will be running a different software version. While the RPs are running different software versions, the mode will change to either RPR or RPR+, depending on the device. The device will change to SSO mode once the upgrade has completed.

• On the Cisco 7500 series router, the previously active processor is being reset and reloaded before the core dump completes--Use the crashdump-timeout command to set the maximum time that the newly active processor waits before resetting and reloading the previously active processor.
• You can enter ROM monitor mode by restarting the router and then pressing the Break key or issuing a send break command from a telnet session during the first 60 seconds of startup.The send break function can be useful for experienced users or for users under the direction of a Cisco Technical Assistance Center (TAC) representative to recover from certain system problems or to evaluate the cause of system problems.
• On the Cisco 7500 series router, issuing a send break does not cause a system switchover--This is normal operation on the Cisco 7500 series router. Using send break to break or pause the system is not recommended and may cause unpredictable results. To initiate a manual switchover, use the redundancy force-switchover command.
• You can enter ROM monitor mode by restarting the router and then pressing the Break key or issuing a send break command from a telnet session during the first 60 seconds of startup.The send break function can be useful for experienced users or for users under the direction of a Cisco Technical Assistance Center (TAC) representative to recover from certain system problems or to evaluate the cause of system problems.
• On Cisco 10000 and 12000 series Internet routers, if a standby RP is present, the system will detect the break and complete a switchover; however, this is not the recommended procedure for initiating a switchover. To initiate a manual switchover, use the redundancy force-switchover command.

• Troubleshooting SSO