Cisco�7600 Series Router Software Configuration Guide Cisco IOS Release 15S
Configuring NSF with SSO Supervisor Engine Redundancy
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Table Of Contents

Configuring NSF with SSO Supervisor Engine Redundancy

Understanding NSF with SSO Supervisor Engine Redundancy

NSF with SSO Supervisor Engine Redundancy Overview

SSO Operation

NSF Operation

Cisco Express Forwarding

Multicast MLS NSF with SSO

Routing Protocols

BGP Operation

OSPF Operation

IS-IS Operation

EIGRP Operation

NSF Benefits and Restrictions

SSO-aware Virtual Router Redundancy Protocol

Supervisor Engine Configuration Synchronization

Supervisor Engine Redundancy Guidelines and Restrictions

Redundancy Configuration Guidelines and Restrictions

Hardware Configuration Guidelines and Restrictions

Configuration Mode Restrictions

NSF Configuration Tasks

Configuring SSO

Configuring Multicast MLS NSF with SSO

Verifying Multicast NSF with SSO

Configuring CEF NSF

Verifying CEF NSF

Configuring BGP NSF

Verifying BGP NSF

Configuring OSPF NSF

Verifying OSPF NSF

Configuring IS-IS NSF

Verifying IS-IS NSF

Configuring EIGRP NSF

Verifying EIGRP NSF

Synchronizing the Supervisor Engine Configurations

Copying Files to the Redundant Supervisor Engine


Configuring NSF with SSO Supervisor Engine Redundancy


This chapter describes how to configure supervisor engine redundancy using Cisco nonstop forwarding (NSF) with stateful switchover (SSO).


NoteFor complete syntax and usage information for the commands used in this chapter, refer to the Cisco 7600 Series Routers Command References at this URL:

http://www.cisco.com/en/US/products/hw/routers/ps368/prod_command_reference_list.html

NSF with SSO does not support IPv6 multicast traffic. However, for information about how to configure supervisor engine redundancy using route processor redundancy (RPR) and RPR+ (which does support IPv6 multicast traffic), see Chapter 7 "Configuring RPR and RPR+ Supervisor Engine Redundancy."

Release 12.2SR does not support single router mode (SRM) with SSO.


This chapter contains these sections:

Understanding NSF with SSO Supervisor Engine Redundancy

Supervisor Engine Configuration Synchronization

NSF Configuration Tasks

Copying Files to the Redundant Supervisor Engine

Understanding NSF with SSO Supervisor Engine Redundancy

These sections describe supervisor engine redundancy using NSF with SSO:

NSF with SSO Supervisor Engine Redundancy Overview

SSO Operation

NSF Operation

Cisco Express Forwarding

Multicast MLS NSF with SSO

Routing Protocols

NSF Benefits and Restrictions

NSF with SSO Supervisor Engine Redundancy Overview


Note With a Supervisor Engine 720, if all of the installed switching modules have DFCs, enter the fabric switching-mode allow dcef-only command to disable the Ethernet ports on both supervisor engines, which ensures that all modules are operating in dCEF mode and simplifies switchover to the redundant supervisor engine. (CSCec05612)
Post SRE release, the uplink ports are also enabled in dcef mode for RSP720-10G supervisor engine. The other supervisor engines continue to have the uplink ports disabled.


Cisco 7600 series routers support fault resistance by allowing a redundant supervisor engine to take over if the primary supervisor engine fails. Cisco NSF works with SSO to minimize the amount of time a network is unavailable to its users following a switchover while continuing to forward IP packets. Cisco 7600 series routers also support route processor redundancy (RPR), route processor redundancy plus (RPR+). For information about these redundancy modes, see Chapter 7 "Configuring RPR and RPR+ Supervisor Engine Redundancy."

The following events cause a switchover:

A hardware failure on the active supervisor engine

Clock synchronization failure between supervisor engines

A manual switchover

SSO Operation

SSO establishes one of the supervisor engines as active while the other supervisor engine is designated as standby, and then SSO synchronizes information between them. A switchover from the active to the redundant supervisor engine occurs when the active supervisor engine fails, or is removed from the router, or is manually shut down for maintenance. This type of switchover ensures that Layer 2 traffic is not interrupted.

In networking devices running SSO, both supervisor engines must be running the same configuration so that the redundant supervisor engine is always ready to assume control following a fault on the active supervisor engine. SSO switchover also preserves FIB and adjacency entries and can forward Layer 3 traffic after a switchover. Configuration information and data structures are synchronized from the active to the redundant supervisor engine at startup and whenever changes to the active supervisor engine configuration occur. Following an initial synchronization between the two supervisor engines, SSO maintains state information between them, including forwarding information.

During switchover, system control and routing protocol execution is transferred from the active supervisor engine to the redundant supervisor engine. The switch requires between 0 and 3 seconds to switchover from the active to the redundant supervisor engine.

NSF Operation

Cisco NSF always runs with SSO and provides redundancy for Layer 3 traffic. NSF works with SSO to minimize the amount of time that a network is unavailable to its users following a switchover. The main purpose of NSF is to continue forwarding IP packets following a supervisor engine switchover.

Cisco NSF is supported by the BGP, OSPF, and IS-IS protocols for routing and is supported by Cisco Express Forwarding (CEF) for forwarding. The routing protocols have been enhanced with NSF-capability and awareness, which means that routers running these protocols can detect a switchover and take the necessary actions to continue forwarding network traffic and to recover route information from the peer devices. The IS-IS protocol can be configured to use state information that has been synchronized between the active and the redundant supervisor engine to recover route information following a switchover instead of information received from peer devices.

A networking device is NSF-aware if it is running NSF-compatible software. A device is NSF-capable if it has been configured to support NSF; it will rebuild routing information from NSF-aware or NSF-capable neighbors.

Each protocol depends on CEF to continue forwarding packets during switchover while the routing protocols rebuild the Routing Information Base (RIB) tables. After the routing protocols have converged, CEF updates the FIB table and removes stale route entries. CEF then updates the line cards with the new FIB information.

Cisco Express Forwarding

A key element of NSF is packet forwarding. In a Cisco networking device, packet forwarding is provided by Cisco Express Forwarding (CEF). CEF maintains the FIB, and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. This feature reduces traffic interruption during the switchover.

During normal NSF operation, CEF on the active supervisor engine synchronizes its current FIB and adjacency databases with the FIB and adjacency databases on the redundant supervisor engine. Upon switchover of the active supervisor engine, the redundant supervisor engine initially has FIB and adjacency databases that are mirror images of those that were current on the active supervisor engine. For platforms with intelligent line cards, the line cards will maintain the current forwarding information over a switchover. For platforms with forwarding engines, CEF will keep the forwarding engine on the redundant supervisor engine current with changes that are sent to it by CEF on the active supervisor engine. The line cards or forwarding engines will be able to continue forwarding after a switchover as soon as the interfaces and a data path are available.

As the routing protocols start to repopulate the RIB on a prefix-by-prefix basis, the updates will cause prefix-by-prefix updates to CEF, which it uses to update the FIB and adjacency databases. Existing and new entries will receive the new version ("epoch") number, indicating that they have been refreshed. The forwarding information is updated on the line cards or forwarding engine during convergence. The supervisor engine signals when the RIB has converged. The software removes all FIB and adjacency entries that have an epoch older than the current switchover epoch. The FIB now represents the newest routing protocol forwarding information.

Multicast MLS NSF with SSO


Note NSF with SSO does not support IPv6 multicast traffic. If you configure support for IPv6 multicast traffic, configure RPR or RPR+ redundancy.


Multicast multilayer switching (MMLS) NSF with SSO is required so that Layer 3 multicast traffic that is switched by the router is not dropped during switchover. Without MMLS NSF with SSO, the Layer 3 multicast traffic is dropped until the multicast protocols converge.

During the switchover process, traffic is forwarded using the old database (from the previously active supervisor engine). After multicast routing protocol convergence has taken place, the shortcuts downloaded by the newly active MSFC will be merged with the existing flows and marked as new shortcuts. Stale entries will slowly be purged from the database allowing NSF to function during the switchover while ensuring a smooth transition to the new cache.

Because multicast routing protocols such as Protocol Independent Multicast (PIM) sparse mode and PIM dense mode are data driven, multicast packets are leaked to the router during switchover so that the protocols can converge.

Because the traffic does not need to be forwarded by software for control-driven protocols such as bidirectional PIM, the router will continue to leak packets using the old cache for these protocols. The router builds the mroute cache and installs the shortcuts in hardware. After the new routes are learned, a timer is triggered to go through the database and purge the old flows.


Note Multicast MLS NSF with SSO requires NSF support in the unicast protocols.


Routing Protocols

The routing protocols run only on the MSFC of the active supervisor engine, and they receive routing updates from their neighbor routers. Routing protocols do not run on the MSFC of the redundant supervisor engine. Following a switchover, the routing protocols request that the NSF-aware neighbor devices send state information to help rebuild the routing tables. Alternately, the IS-IS protocol can be configured to synchronize state information from the active to the redundant supervisor engine to help rebuild the routing table on the NSF-capable device in environments where neighbor devices are not NSF-aware. Cisco NSF supports the BGP, OSPF, IS-IS, and EIGRP protocols


Note For NSF operation, the routing protocols depend on CEF to continue forwarding packets while the routing protocols rebuild the routing information.


BGP Operation

When an NSF-capable router begins a BGP session with a BGP peer, it sends an OPEN message to the peer. Included in the message is a statement that the NSF-capable device has "graceful" restart capability. Graceful restart is the mechanism by which BGP routing peers avoid a routing flap following a switchover. If the BGP peer has received this capability, it is aware that the device sending the message is NSF-capable. Both the NSF-capable router and its BGP peers need to exchange the graceful restart capability in their OPEN messages at the time of session establishment. If both the peers do not exchange the graceful restart capability, the session will not be graceful restart capable.

If the BGP session is lost during the supervisor engine switchover, the NSF-aware BGP peer marks all the routes associated with the NSF-capable router as stale; however, it continues to use these routes to make forwarding decisions for a set period of time. This functionality prevents packets from being lost while the newly active supervisor engine is waiting for convergence of the routing information with the BGP peers.

After a supervisor engine switchover occurs, the NSF-capable router reestablishes the session with the BGP peer. In establishing the new session, it sends a new graceful restart message that identifies the NSF-capable router as having restarted.

At this point, the routing information is exchanged between the two BGP peers. After this exchange is complete, the NSF-capable device uses the routing information to update the RIB and the FIB with the new forwarding information. The NSF-aware device uses the network information to remove stale routes from its BGP table; the BGP protocol then is fully converged.

If a BGP peer does not support the graceful restart capability, it will ignore the graceful restart capability in an OPEN message but will establish a BGP session with the NSF-capable device. This function will allow interoperability with non-NSF-aware BGP peers (and without NSF functionality), but the BGP session with non-NSF-aware BGP peers will not be graceful restart capable.


Note BGP support in NSF requires that neighbor networking devices be NSF-aware; that is, the devices must have the graceful restart capability and advertise that capability in their OPEN message during session establishment. If an NSF-capable router discovers that a particular BGP neighbor does not have graceful restart capability, it will not establish an NSF-capable session with that neighbor. All other neighbors that have graceful restart capability will continue to have NSF-capable sessions with this NSF-capable networking device.


OSPF Operation

When an OSPF NSF-capable router performs a supervisor engine switchover, it must perform the following tasks in order to resynchronize its link state database with its OSPF neighbors:

Relearn the available OSPF neighbors on the network without causing a reset of the neighbor relationship

Reacquire the contents of the link state database for the network

As quickly as possible after a supervisor engine switchover, the NSF-capable router sends an OSPF NSF signal to neighboring NSF-aware devices. Neighbor networking devices recognize this signal as an indicator that the neighbor relationship with this router should not be reset. As the NSF-capable router receives signals from other routers on the network, it can begin to rebuild its neighbor list.

After neighbor relationships are reestablished, the NSF-capable router begins to resynchronize its database with all of its NSF-aware neighbors. At this point, the routing information is exchanged between the OSPF neighbors. Once this exchange is complete, the NSF-capable device uses the routing information to remove stale routes, update the RIB, and update the FIB with the new forwarding information. The OSPF protocols are then fully converged.


Note OSPF NSF requires that all neighbor networking devices be NSF-aware. If an NSF-capable router discovers that it has non-NSF -aware neighbors on a particular network segment, it will disable NSF capabilities for that segment. Other network segments composed entirely of NSF-capable or NSF-aware routers will continue to provide NSF capabilities.


IS-IS Operation

When an IS-IS NSF-capable router performs a supervisor engine switchover, it must perform the following tasks in order to resynchronize its link state database with its IS-IS neighbors:

Relearn the available IS-IS neighbors on the network without causing a reset of the neighbor relationship

Reacquire the contents of the link state database for the network

The IS-IS NSF feature offers two options when you configure NSF:

Internet Engineering Task Force (IETF) IS-IS

Cisco IS-IS

If neighbor routers on a network segment are running a software version that supports the IETF Internet draft for router restartability, they will assist an IETF NSF router that is restarting. With IETF, neighbor routers provide adjacency and link-state information to help rebuild the routing information following a switchover. A benefit of IETF IS-IS configuration is operation between peer devices based on a proposed standard.


Note If you configure IETF on the networking device, but neighbor routers are not IETF-compatible, NSF will abort following a switchover.


If the neighbor routers on a network segment are not NSF-aware, you must use the Cisco configuration option. The Cisco IS-IS configuration transfers both protocol adjacency and link-state information from the active to the redundant supervisor engine. An advantage of Cisco configuration is that it does not rely on NSF-aware neighbors.

IETF IS-IS Configuration

As quickly as possible after a supervisor engine switchover, the NSF-capable router sends IS-IS NSF restart requests to neighboring NSF-aware devices using the IETF IS-IS configuration. Neighbor networking devices recognize this restart request as an indicator that the neighbor relationship with this router should not be reset, but that they should initiate database resynchronization with the restarting router. As the restarting router receives restart request responses from routers on the network, it can begin to rebuild its neighbor list.

After this exchange is complete, the NSF-capable device uses the link-state information to remove stale routes, update the RIB, and update the FIB with the new forwarding information; IS-IS is then fully converged.

The switchover from one supervisor engine to the other happens within seconds. IS-IS reestablishes its routing table and resynchronizes with the network within a few additional seconds. At this point, IS-IS waits for a specified interval before it will attempt a second NSF restart. During this time, the new redundant supervisor engine will boot up and synchronize its configuration with the active supervisor engine. The IS-IS NSF operation waits for a specified interval to ensure that connections are stable before attempting another restart of IS-IS NSF. This functionality prevents IS-IS from attempting back-to-back NSF restarts with stale information.

Cisco IS-IS Configuration

Using the Cisco configuration option, full adjacency and LSP information is saved, or checkpointed, to the redundant supervisor engine. Following a switchover, the newly active supervisor engine maintains its adjacencies using the check-pointed data, and can quickly rebuild its routing tables.


Note Following a switchover, Cisco IS-IS NSF has complete neighbor adjacency and LSP information; however, it must wait for all interfaces to come on line that had adjacencies prior to the switchover. If an interface does not come on line within the allocated interface wait time, the routes learned from these neighbor devices are not considered in routing table recalculation. IS-IS NSF provides a command to extend the wait time for interfaces that, for whatever reason, do not come on line in a timely fashion.


The switchover from one supervisor engine to the other happens within seconds. IS-IS reestablishes its routing table and resynchronizes with the network within a few additional seconds. At this point, IS-IS waits for a specified interval before it will attempt a second NSF restart. During this time, the new redundant supervisor engine will boot up and synchronize its configuration with the active supervisor engine. After this synchronization is completed, IS-IS adjacency and LSP data is check-pointed to the redundant supervisor engine; however, a new NSF restart will not be attempted by IS-IS until the interval time expires. This functionality prevents IS-IS from attempting back-to-back NSF restarts.


Note Effective with Cisco IOS Release 15.2(4)S, Cisco 7600 series routers support RFC 6213. If you configure IS-IS to use BFD on an interface, the BFD session must come up before the IS-IS adjacency comes up. If the BFD session is down, then the ISIS adjacency will not come up.


EIGRP Operation

When an EIGRP NSF-capable router initially comes back up from an NSF restart, it has no neighbor and its topology table is empty. The router is notified by the redundant (now active) supervisor engine when it needs to bring up the interfaces, reacquire neighbors, and rebuild the topology and routing tables. The restarting router and its peers must accomplish these tasks without interrupting the data traffic directed toward the restarting router. EIGRP peer routers maintain the routes learned from the restarting router and continue forwarding traffic through the NSF restart process.

To prevent an adjacency reset by the neighbors, the restarting router will use a new Restart (RS) bit in the EIGRP packet header to indicate a restart. The RS bit will be set in the hello packets and in the initial INIT update packets during the NSF restart period. The RS bit in the hello packets allows the neighbors to be quickly notified of the NSF restart. Without seeing the RS bit, the neighbor can only detect an adjacency reset by receiving an INIT update or by the expiration of the hello hold timer. Without the RS bit, a neighbor does not know if the adjacency reset should be handled using NSF or the normal startup method.

When the neighbor receives the restart indication, either by receiving the hello packet or the INIT packet, it will recognize the restarting peer in its peer list and will maintain the adjacency with the restarting router. The neighbor then sends it topology table to the restarting router with the RS bit set in the first update packet indicating that it is NSF-aware and is helping out the restarting router. The neighbor does not set the RS bit in their hello packets, unless it is also a NSF restarting neighbor.


Note A router may be NSF-aware but may not be participating in helping out the NSF restarting neighbor because it is coming up from a cold start.


If at least one of the peer routers is NSF-aware, the restarting router would then receive updates and rebuild its database. The restarting router must then find out if it had converged so that it can notify the routing information base (RIB). Each NSF-aware router is required to send an end of table (EOT) marker in the last update packet to indicate the end of the table content. The restarting router knows it has converged when it receives the EOT marker. The restarting router can then begin sending updates.

An NSF-aware peer would know when the restarting router had converged when it receives an EOT indication from the restarting router. The peer then scans its topology table to search for the routes with the restarted neighbor as the source. The peer compares the route timestamp with the restart event timestamp to determine if the route is still available. The peer then goes active to find alternate paths for the routes that are no longer available through the restarted router.

When the restarting router has received all EOT indications from its neighbors or when the NSF converge timer expires, EIGRP will notify the RIB of convergence. EIGRP waits for the RIB convergence signal and then floods its topology table to all awaiting NSF-aware peers.

NSF Benefits and Restrictions

Cisco NSF provides these benefits:

Improved network availability

NSF continues forwarding network traffic and application state information so that user session information is maintained after a switchover.

Overall network stability

Network stability may be improved with the reduction in the number of route flaps that had been created when routers in the network failed and lost their routing tables.

Neighboring routers do not detect a link flap

Because the interfaces remain up throughout a switchover, neighboring routers do not detect a link flap (the link does not go down and come back up).

Prevents routing flaps

Because SSO continues forwarding network traffic in the event of a switchover, routing flaps are avoided.

No loss of user sessions

User sessions established before the switchover are maintained.

Cisco NSF with SSO has these restrictions:

For NSF operation, you must have SSO configured on the device.

NSF with SSO supports IP Version 4 traffic and protocols only.

Enhanced Object Tracking is not SSO-aware and cannot be used with Hot Standby Routing Protocol (HSRP), Virtual Router Redundancy Protocol (VRRP), or Gateway Load Balancing Protocol (GLBP) in SSO mode.

All neighboring devices participating in BGP NSF must be NSF-capable and configured for BGP graceful restart.

OSPF NSF for virtual links is not supported.

All OSPF networking devices on the same network segment must be NSF-aware (running an NSF software image).

For IETF IS-IS, all neighboring devices must be running an NSF-aware software image.

IPv4 Multicast NSF with SSO is supported by the PFC3 only.

The underlying unicast protocols must be NSF-aware in order to use multicast NSF with SSO.

Starting from Release 12.2(33)SRE, bidirectional forwarding detection (BFD) is SSO-aware and is supported by NSF with SSO.

SSO-aware Virtual Router Redundancy Protocol

The Stateful Switchover (SSO) - aware Virtual Router Redundancy Protocol (VRRP) feature enables the Cisco IOS VRRP subsystem software detect the following:

Installation of a standby Route Processor (RP)

Configuration of the system in the SSO redundancy mode

In the event of an active RP failure, the VRRP group itself remains unchanged, and traffic continues to be forwarded through the current active gateway router. The SSO-aware VRRP feature preserves the forwarding path for traffic destined to VRRP virtual IP through an RP switchover. Configuring SSO on the edge router enables the traffic on the Ethernet links to continue during an RP failover: Ethernet traffic requires no switchover to another VRRP router. During a switchover, the synchronization of VRRP SSO information to the standby RP allows the continuous forwarding of the traffic that is sent with the VRRP virtual IP address without loss of data or path change.


Note The addition of SSO to the VRRP redundancy scheme provides high availability of gateway.


Supervisor Engine Configuration Synchronization

These sections describe supervisor engine configuration synchronization:

Supervisor Engine Redundancy Guidelines and Restrictions

Redundancy Configuration Guidelines and Restrictions


Note Configuration changes made through SNMP are not synchronized to the redundant supervisor engine. After you configure the router through SNMP, copy the running-config file to the startup-config file on the active supervisor engine to trigger synchronization of the startup-config file on the redundant supervisor engine.


Supervisor Engine Redundancy Guidelines and Restrictions

These sections describe supervisor engine redundancy guidelines and restrictions:

Redundancy Configuration Guidelines and Restrictions

Hardware Configuration Guidelines and Restrictions

Configuration Mode Restrictions

Redundancy Configuration Guidelines and Restrictions

These guidelines and restrictions apply to all redundancy modes:

With a Supervisor Engine 720, if all the installed switching modules have DFCs, enter the fabric switching-mode allow dcef-only command to disable the Ethernet ports on both supervisor engines, which ensures that all modules are operating in dCEF mode and simplifies switchover to the redundant supervisor engine.

Post SRE release, the uplink ports are also enabled in dcef mode for RSP720-10G supervisor engine. The other supervisor engines continue to have the uplink ports disabled.s

Supervisor engine redundancy does not provide supervisor engine mirroring or supervisor engine load balancing. Only one supervisor engine is active.

Configuration changes made through SNMP are not synchronized to the redundant supervisor engine. After you configure the router through SNMP, copy the running-config file to the startup-config file on the active supervisor engine to trigger synchronization of the startup-config file on the redundant supervisor engine.

Supervisor engine switchover takes place after the failed supervisor engine completes a core dump. A core dump can take up to 15 minutes. To get faster switchover time, disable core dump on the supervisor engines.

With a Supervisor Engine 720, if a fabric synchronization error occurs, the default behavior is to switchover to the redundant supervisor engine. In some cases, a switchover to the redundant supervisor engine is more disruptive than powering down the module that caused the fabric synchronization error. Enter the no fabric error-recovery fabric-switchover command to disable the switchover and power down the module with the fabric synchronization error.

Hardware Configuration Guidelines and Restrictions

For redundant operation, the following guidelines and restrictions must be met:

Cisco IOS software running on the supervisor engine and the MSFC supports redundant configurations when the supervisor engines and MSFC routers are identical. If they are not identical, one will boot first and become active and hold the other supervisor engine and MSFC in a reset condition.

Each supervisor engine must have the resources to run the router on its own, which means all supervisor engine resources are duplicated, including all Flash devices.

Make separate console connections to each supervisor engine. Do not connect a Y cable to the console ports.

Both supervisor engines must have the same system image (see the "Copying Files to the Redundant Supervisor Engine" section).


Note If a newly installed redundant supervisor engine has the Catalyst operating system installed, remove the active supervisor engine and boot the router with only the redundant supervisor engine installed. Follow the procedures in the current release notes to convert the redundant supervisor engine from the Catalyst operating system.


The configuration register in the startup-config must be set to autoboot.


Note There is no support for booting from the network.


Configuration Mode Restrictions

The following configuration restrictions apply during the startup synchronization process:

You cannot perform configuration changes during the startup (bulk) synchronization. If you attempt to make configuration changes during this process, the following message is generated:

Config mode locked out till standby initializes
 
 

If configuration changes occur at the same time as a supervisor engine switchover, these configuration changes are lost.

NSF Configuration Tasks

The following sections describe the configuration tasks for the NSF feature:

Configuring SSO

Configuring Multicast MLS NSF with SSO

Verifying Multicast NSF with SSO

Configuring CEF NSF

Verifying CEF NSF

Configuring BGP NSF

Verifying BGP NSF

Configuring OSPF NSF

Verifying OSPF NSF

Configuring IS-IS NSF

Verifying IS-IS NSF

Configuring SSO

You must configure SSO in order to use NSF with any supported protocol. To configure SSO, perform this task:

 
Command
Purpose

Step 1 

Router(config)# redundancy

Enters redundancy configuration mode.

Step 2 

Router(config-red)# mode sso

Configures SSO. When this command is entered, the redundant supervisor engine is reloaded and begins to work in SSO mode.

Step 3 

Router# show running-config

Verifies that SSO is enabled.

Step 4 

Router# show redundancy states

Displays the operating redundancy mode.

This example shows how to configure the system for SSO and display the redundancy state:

Router> enable 
Router# configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)# redundancy 
Router(config-red)# mode sso 
Router(config-red)# end 
Router# show redundancy states 
my state = 13 -ACTIVE
     peer state = 8  -STANDBY HOT
           Mode = Duplex
           Unit = Primary
        Unit ID = 5
 
 
Redundancy Mode (Operational) = sso
Redundancy Mode (Configured)  = sso
     Split Mode = Disabled
   Manual Swact = Enabled
 Communications = Up
 
 
   client count = 29
 client_notification_TMR = 30000 milliseconds
          keep_alive TMR = 9000 milliseconds
        keep_alive count = 1
    keep_alive threshold = 18
           RF debug mask = 0x0
Router#

Configuring Multicast MLS NSF with SSO


Note The commands in this section are optional and can be used to customize your configuration. For most users, the default settings are adequate.


Multicast MLS NSF with SSO is on by default when SSO is selected as the redundancy mode. To configure multicast NSF with SSO parameters, perform this task:

 
Command
Purpose

Step 1 

Router# configure terminal

Enters global configuration mode.

Step 2 

Router(config)# mls ip multicast sso convergence-time time

Specifies the maximum time to wait for protocol convergence; valid values are from 0 to 3600 seconds.

Step 3 

Router(config)# mls ip multicast sso leak interval

Specifies the packet leak interval; valid values are from 0 to 3600 seconds. For PIM sparse mode and PIM dense mode this is the period of time after which packet leaking for existing PIM sparse mode and PIM dense mode multicast forwarding entries should be completed.

Step 4 

Router(config)# mls ip multicast sso leak percentage

Specifies the percentage of multicast flows; valid values are from 1 to 100 percent. The value represents the percentage of the total number of existing PIM sparse mode and PIM dense mode multicast flows that should be flagged for packet leaking.

Verifying Multicast NSF with SSO

To verify the multicast NSF with SSO settings, enter the show mls ip multicast sso command:

router# show mls ip multicast sso
Multicast SSO is enabled
Multicast HA Parameters
---------------------------------------------------+------+
protocol convergence timeout                       120 secs
flow leak percent                                  10
flow leak interval                                 60 secs

Configuring CEF NSF

The CEF NSF feature operates by default while the networking device is running in SSO mode. No configuration is necessary.

Verifying CEF NSF

To verify that CEF is NSF-capable, enter the show cef state command:

router# show cef state
 
 
CEF Status [RP]
CEF enabled/running
dCEF enabled/running
CEF switching enabled/running
CEF default capabilities:
Always FIB switching:      yes
Default CEF switching:     yes
Default dCEF switching:    yes
Update HWIDB counters:     no
Drop multicast packets:    no
.
.
.
CEF NSF capable:           yes
IPC delayed func on SSO:   no
RRP state:   
I am standby RRP:          no
My logical slot:           0
RF PeerComm:               no

Configuring BGP NSF


Note You must configure BGP graceful restart on all peer devices participating in BGP NSF.


To configure BGP for NSF, perform this task on each of the BGP NSF peer devices:

 
Command
Purpose

Step 1 

Router# configure terminal

Enters global configuration mode.

Step 2 

Router(config)# router bgp as-number

Enables a BGP routing process, which places the router in router configuration mode.

Step 3 

Router(config-router)# bgp graceful-restart

Enables the BGP graceful restart capability, starting BGP NSF.

If you enter this command after the BGP session has been established, you must restart the session for the capability to be exchanged with the BGP neighbor.

Use this command on the restarting router and all of its peers.

Verifying BGP NSF

To verify BGP NSF, you must check that the graceful restart function is configured on the SSO-enabled networking device and on the neighbor devices. To verify, follow these steps:


Step 1 Verify that "bgp graceful-restart" appears in the BGP configuration of the SSO-enabled router by entering the show running-config command:

Router# show running-config
 
 
.
.
.
router bgp 120
.
.
.
bgp graceful-restart
 neighbor 10.2.2.2 remote-as 300
.
.
.

Step 2 Repeat step 1 on each of the BGP neighbors.

Step 3 On the SSO device and the neighbor device, verify that the graceful restart function is shown as both advertised and received, and confirm the address families that have the graceful restart capability. If no address families are listed, then BGP NSF also will not occur:

router#show ip bgp neighbors x.x.x.x
 
 
BGP neighbor is 192.168.2.2,  remote AS YY, external link
  BGP version 4, remote router ID 192.168.2.2
  BGP state = Established, up for 00:01:18
  Last read 00:00:17, hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    Route refresh:advertised and received(new)
    Address family IPv4 Unicast:advertised and received
    Address family IPv4 Multicast:advertised and received
    Graceful Restart Capabilty:advertised and received
      Remote Restart timer is 120 seconds
      Address families preserved by peer:
        IPv4 Unicast, IPv4 Multicast
  Received 1539 messages, 0 notifications, 0 in queue
  Sent 1544 messages, 0 notifications, 0 in queue
  Default minimum time between advertisement runs is 30 seconds
 
 

Configuring OSPF NSF


Note All peer devices participating in OSPF NSF must be made OSPF NSF-aware, which happens automatically once you install an NSF software image on the device.


To configure OSPF NSF, perform this task:

 
Command
Purpose

Step 1 

Router# configure terminal

Enters global configuration mode.

Step 2 

Router(config)# router ospf processID

Enables an OSPF routing process, which places the router in router configuration mode.

Step 3 

Router(config-router)# nsf

Enables NSF operations for OSPF.

Verifying OSPF NSF

To verify OSPF NSF, you must check that the NSF function is configured on the SSO-enabled networking device. To verify OSPF NSF, follow these steps:


Step 1 Verify that `nsf' appears in the OSPF configuration of the SSO-enabled device by entering the show running-config command:

Router# show running-config
 
 
router ospf 120
log-adjacency-changes
nsf
network 192.168.20.0 0.0.0.255 area 0
network 192.168.30.0 0.0.0.255 area 1 
network 192.168.40.0 0.0.0.255 area 2 
.
.
.
 
 

Step 2 Enter the show ip ospf command to verify that NSF is enabled on the device:

router> show ip ospf
 
 
Routing Process "ospf 1" with ID 192.168.2.1 and Domain ID 0.0.0.1
Supports only single TOS(TOS0) routes
Supports opaque LSA
SPF schedule delay 5 secs, Hold time between two SPFs 10 secs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
Number of external LSA 0. Checksum Sum 0x0 
Number of opaque AS LSA 0. Checksum Sum 0x0
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Non-Stop Forwarding enabled, last NSF restart 00:02:06 ago (took 44 secs)
Area BACKBONE(0)
Number of interfaces in this area is 1 (0 loopback)
 Area has no authentication
 SPF algorithm executed 3 times

Configuring IS-IS NSF

To configure IS-IS NSF, perform this task:

 
Command
Purpose

Step 1 

Router# configure terminal

Enters global configuration mode.

Step 2 

Router(config)# router isis [tag]

Enables an IS-IS routing process, which places the router in router configuration mode.

Step 3 

Router(config-router)# nsf [cisco | ietf]

Enables NSF operation for IS-IS.

Enter the ietf keyword to enable IS-IS in a homogeneous network where adjacencies with networking devices supporting IETF draft-based restartability is guaranteed.

Enter the cisco keyword to run IS-IS in heterogeneous networks that might not have adjacencies with NSF-aware networking devices.

Step 4 

Router(config-router)# nsf interval [minutes]

(Optional) Specifies the minimum time between NSF restart attempts. The default time between consecutive NSF restart attempts is 5 minutes.

Step 5 

Router(config-router)# nsf t3 {manual [seconds] | adjacency}

(Optional) Specifies the time IS-IS will wait for the IS-IS database to synchronize before generating overloaded link-state information for itself and flooding that information out to its neighbors.

The t3 keyword applies only if you selected IETF operation. When you specify adjacency, the router that is restarting obtains its wait time from neighboring devices.

Step 6 

Router(config-router)# nsf interface wait seconds

(Optional) Specifies how long an IS-IS NSF restart will wait for all interfaces with IS-IS adjacencies to come up before completing the restart. The default is 10 seconds.

Verifying IS-IS NSF

To verify IS-IS NSF, you must check that the NSF function is configured on the SSO-enabled networking device. To verify IS-IS NSF, follow these steps:


Step 1 Verify that "nsf" appears in the IS-IS configuration of the SSO-enabled device by entering the show running-config command. The display will show either the Cisco IS-IS or the IETF IS-IS configuration. The following display indicates that the device uses the Cisco implementation of IS-IS NSF:

Router# show running-config
<...Output Truncated...>
router isis 
nsf cisco
<...Output Truncated...>
 
 

Step 2 If the NSF configuration is set to cisco, enter the show isis nsf command to verify that NSF is enabled on the device. Using the Cisco configuration, the display output will be different on the active and redundant  RPs. The following display shows sample output for the Cisco configuration on the active RP. In this example, note the presence of "NSF restart enabled":

router# show isis nsf 
 
 
NSF is ENABLED, mode 'cisco'
 
 
RP is ACTIVE, standby ready, bulk sync complete
NSF interval timer expired (NSF restart enabled)
Checkpointing enabled, no errors
Local state:ACTIVE,  Peer state:STANDBY HOT,  Mode:SSO
 
 

The following display shows sample output for the Cisco configuration on the standby RP. In this example, note the presence of "NSF restart enabled":

router# show isis nsf 
 
 
NSF enabled, mode 'cisco'
RP is STANDBY, chkpt msg receive count:ADJ 2, LSP 7
NSF interval timer notification received (NSF restart enabled)
Checkpointing enabled, no errors
Local state:STANDBY HOT,  Peer state:ACTIVE,  Mode:SSO
 
 

Step 3 If the NSF configuration is set to ietf, enter the show isis nsf command to verify that NSF is enabled on the device. The following display shows sample output for the IETF IS-IS configuration on the networking device:

router# show isis nsf 
 
 
NSF is ENABLED, mode IETF 
NSF pdb state:Inactive
NSF L1 active interfaces:0
NSF L1 active LSPs:0
NSF interfaces awaiting L1 CSNP:0
Awaiting L1 LSPs:
NSF L2 active interfaces:0
NSF L2 active LSPs:0
NSF interfaces awaiting L2 CSNP:0
Awaiting L2 LSPs:
Interface:Serial3/0/2
    NSF L1 Restart state:Running
    NSF p2p Restart retransmissions:0
    Maximum L1 NSF Restart retransmissions:3
    L1 NSF ACK requested:FALSE
    L1 NSF CSNP requested:FALSE
    NSF L2 Restart state:Running
    NSF p2p Restart retransmissions:0
    Maximum L2 NSF Restart retransmissions:3
    L2 NSF ACK requested:FALSE
Interface:GigabitEthernet2/0/0
    NSF L1 Restart state:Running
    NSF L1 Restart retransmissions:0
    Maximum L1 NSF Restart retransmissions:3
    L1 NSF ACK requested:FALSE
    L1 NSF CSNP requested:FALSE
    NSF L2 Restart state:Running
    NSF L2 Restart retransmissions:0
    Maximum L2 NSF Restart retransmissions:3
    L2 NSF ACK requested:FALSE
    L2 NSF CSNP requested:FALSE
Interface:Loopback1
    NSF L1 Restart state:Running
    NSF L1 Restart retransmissions:0
    Maximum L1 NSF Restart retransmissions:3
    L1 NSF ACK requested:FALSE
    L1 NSF CSNP requested:FALSE
    NSF L2 Restart state:Running
    NSF L2 Restart retransmissions:0
    Maximum L2 NSF Restart retransmissions:3
    L2 NSF ACK requested:FALSE
    L2 NSF CSNP requested:FALSE
 
 

Configuring EIGRP NSF

To configure EIGRP NSF, perform this task:

 
Command
Purpose

Step 1 

Router# configure terminal

Enters global configuration mode.

Step 2 

Router(config)# router eigrp as-number

Enables an EIGRP routing process, which places the router in router configuration mode.

Step 3 

Router(config-router)# nsf

Enables EIGRP NSF.

Use this command on the restarting router and all of its peers.

Verifying EIGRP NSF

To verify EIGRP NSF, you must check that the NSF function is configured on the SSO-enabled networking device. To verify EIGRP NSF, follow these steps:


Step 1 Verify that "nsf" appears in the EIGRP configuration of the SSO-enabled device by entering the show running-config command:

Router# show running-config
.
.
.
router eigrp 100
 auto-summary
 nsf 
.
.
.

Step 2 Enter the show ip protocols command to verify that NSF is enabled on the device:

Router# show ip protocols 
*** IP Routing is NSF aware ***
Routing Protocol is "eigrp 100"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Default networks accepted from incoming updates
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  EIGRP maximum hopcount 100
  EIGRP maximum metric variance 1
  Redistributing: eigrp 100
  EIGRP NSF-aware route hold timer is 240s
  EIGRP NSF enabled
     NSF signal timer is 20s
     NSF converge timer is 120s
  Automatic network summarization is in effect
  Maximum path: 4
  Routing for Networks:
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: internal 90 external 170
 
 

Synchronizing the Supervisor Engine Configurations

During normal operation, the startup-config and config-registers configurations are synchronized by default between the two supervisor engines. In a switchover, the new active supervisor engine uses the current configuration.

Copying Files to the Redundant Supervisor Engine

Enter this command to copy a file to the disk0: device on a redundant supervisor engine:

Router# copy source_device:source_filename slavedisk0:target_filename 
 
 

Enter this command to copy a file to the bootflash: device on a redundant supervisor engine:

Router# copy source_device:source_filename slavesup-bootflash:target_filename 
 
 

Enter this command to copy a file to the bootflash: device on a redundant MSFC:

Router# copy source_device:source_filename slavebootflash:target_filename