Cisco Systems 4500 NSF with SSO, OSPF for Routed Access, Policy-Based Routing, Unidirectional Link Routing

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Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 1 Product Overview Layer 3 Software Features
NSF with SSO
Non-Stop Forwarding with Stateful Switchover (NSF/SSO) offers continuous data packet forwarding in
a Layer 3 routing environment during supervisor engine switchover. During supervisor engine
switchover, NSF/SSO continues forwarding data packets along known routes while the routing protocol
information is recovered and validated, avoiding unnecessary route flaps and network instability. With
NSF/SSO, IP phone calls do not drop. NSF/SSO is supported for OSPF, BGP, EIGRP, IS-IS, and Cisco
Express Forwarding (CEF). NSF/SSO is typically deployed in the most critical parts of an enterprise or
service provider network, such as Layer 3 aggregation/core or a resilient Layer 3 wiring closet design.
It is an essential component of single chassis deployment for critical applications. NSF/SSO is available
for all shipping supervisor engines on Catalyst 4507R and 4510R chassis with supervisor redundancy.
For information on NSF with SSO, see Chapter 9, “Configuring Cisco NSF with SSO Supervisor Engine
Redundancy.”
OSPF for Routed Access
OSPF for Routed Access is designed specifically to enable customers to extend Layer 3 routing
capabilities to the access or wiring closet.
Note OSPF for Routed Access supports only one OSPFv2 and one OSPFv3 instance with a maximum number
of 200 dynamically learned routes.
With the typical topology (hub and spoke) in a campus environment, where the wiring closets (spokes)
are connected to the distribution switch (hub) forwarding all nonlocal traffic to the distribution layer, the
wiring closet switch does not need to hold a complete routing table. Ideally, the distribution switch sends
a default route to the wiring closet switch to reach inter-area and external routes (OSPF stub or totally
stub area configuration).
Refer to the following link for more details:
http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/routed-ex.html
With Cisco IOS Release 12.2(53)SG, the IP Base image supports OSPF for routed access. The Enterprise
Services image is required if you need multiple OSPFv2 and OSPFv3 instances without route
restrictions. Enterprise Services also is required to enable the VRF-lite feature.
Policy-Based Routing
Traditional IP forwarding decisions are based purely on the destination IP address of the packet being
forwarded. Policy-Based Routing (PBR) enables forwarding based upon other information associated
with a packet, such as the source interface, IP source address, Layer 4 ports, and so on. This feature
allows network managers more flexibility in how they configure and design their networks.
For more information on policy-based routing, see Chapter 35, “Configuring Policy-Based Routing.”
Unidirectional Link Routing
Unidirectional link routing (UDLR) provides a way to forward multicast packets over a physical
unidirectional interface (such as a satellite link of high bandwidth) to stub networks that have a back
channel.