C H A P T E R 6 Configuring Supervisor Engine Redundancy Using Rpr And Sso; Understanding Cisco Ios Nsf-Awareness Support - Cisco 4500M Software Manual

Understanding Cisco IOS NSF-Awareness Support

Understanding Cisco IOS NSF-Awareness Support
Cisco IOS Nonstop Forwarding (NSF) has two primary components:
NSF capable devices are Catalyst 6500 series switches, Cisco 7500 series routers, Cisco 10000 series
Note
routers, and Cisco 12000 series routers. The Catalyst 4500 series switch is an NSF-aware device for
Release 12.2(20)EWA.
For more information on BGP, EIGRP, OSPF, and IS-IS NSF-awareness, refer to the URL:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guides_list.html
A typical topology for NSF and NSF-aware routers is given below.
Figure 6-1
Catalyst 4500
NSF-Aware
Software Configuration Guide—Release 12.2(25)EW
6-2
NSF-capability—NSF works with SSO to minimize the amount of time that a Layer 3 network is
unavailable following a supervisor engine switchover by continuing to forward IP packets.
Reconvergence of Layer 3 routing protocols (BGP, EIGRP, OSPF v2, and IS-IS) is transparent to the
user and happens automatically in the background. The routing protocols recover routing
information from neighbor devices and rebuild the Cisco Express Forwarding (CEF) table.
NSF-awareness—If neighboring router devices detect that an NSF router can still forward packets
when RP (Route Processor) switchover happens, this capability is referred to as NSF-awareness.
Cisco IOS enhancements to the Layer 3 protocols OSPF, BGP, EIGRP and IS-IS are designed to
prevent route-flapping so that the CEF routing table does not timeout or the NSF router does not
drop routes. An NSF-aware router helps to send routing protocol information to the neighboring
NSF router.
Topology for NSF and NSF-Aware Router
Catalyst 6500 NSF
Si
2
Si
Chapter 6 Configuring Supervisor Engine Redundancy Using RPR and SSO
2
Si
Catalyst 4500
NSF-Aware
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