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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
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Chapter 7 Configuring NSF with SSO Supervisor Engine Redundancy
Understanding NSF with SSO Supervisor Engine Redundancy
•
NSF Operation, page 7-3
•
Cisco Express Forwarding, page 7-3
•
Multicast MLS NSF with SSO, page 7-4
•
Routing Protocols, page 7-4
•
NSF Benefits and Restrictions, page 7-8
NSF with SSO Supervisor Engine Redundancy Overview
Note
•
With Release 12.2(18)SXD and earlier releases, when a redundant supervisor engine is in standby
mode, the two Gigabit Ethernet interfaces on the redundant supervisor engine are always active.
•
With a Supervisor Engine 720 and Release 12.2(18)SXE and later releases, 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. (CSCec05612)
•
With a Supervisor Engine 2 and Release 12.2(18)SXD1 and later releases, if all the installed
switching modules have DFCs, enter the
fabric switching-mode allow dcef-only
command to
disable the Ethernet ports on the redundant supervisor engine, which ensures that all modules are
operating in dCEF mode. (CSCec05612)
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+), and single router mode with stateful switchover (SRM with SSO) for redundancy. For
information about these redundancy modes, see
Chapter 8, “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
