Ospfv2 Stub Router Advertisements; Multiple Ospfv2 Instances; Spf Optimization; Virtualization Support - Cisco Nexus 3000 Series Configuration Manual
Nx-os unicast routing configuration guide,
nx-os release 5.0(3)u1(1)
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- Command reference manual (356 pages) ,
- Configuration manual (182 pages) ,
- Installation manual (112 pages)
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Chapter 3
Configuring OSPFv2
S e n d d o c u m e n t c o m m e n t s t o n e x u s 3 k - d o c f e e d b a c k @ c i s c o . c o m
External route summarization is specific to external routes that are injected into OSPFv2 using route
redistribution. You should make sure that external ranges that are being summarized are contiguous.
Summarizing overlapping ranges from two different routers could cause packets to be sent to the wrong
destination. Configure external route summarization on ASBRs that are redistributing routes into OSPF.
When you configure a summary address, Cisco NX-OS automatically configures a discard route for the
summary address to prevent routing black holes and route loops.
OSPFv2 Stub Router Advertisements
You can configure an OSPFv2 interface to act as a stub router using the OSPFv2 Stub Router
Advertisements feature. Use this feature when you want to limit the OSPFv2 traffic through this router,
such as when you want to introduce a new router to the network in a controlled manner or limit the load
on a router that is already overloaded. You might also want to use this feature for various administrative
or traffic engineering reasons.
OSPFv2 stub router advertisements do not remove the OSPFv2 router from the network topology, but
they do prevent other OSPFv2 routers from using this router to route traffic to other parts of the network.
Only the traffic that is destined for this router or directly connected to this router is sent.
OSPFv2 stub router advertisements mark all stub links (directly connected to the local router) to the cost
of the local OSPFv2 interface. All remote links are marked with the maximum cost (0xFFFF).
Multiple OSPFv2 Instances
Cisco NX-OS supports multiple instances of the OSPFv2 protocol that run on the same node. You cannot
configure multiple instances over the same interface. By default, every instance uses the same system
router ID. You must manually configure the router ID for each instance if the instances are in the same
OSPFv2 autonomous system.
SPF Optimization
Cisco NX-OS optimizes the SPF algorithm in the following ways:
•
•
Virtualization Support
OSPFv2 supports Virtual Routing and Forwarding instances (VRFs). By default, Cisco NX-OS places
you in the default VRF unless you specifically configure another VRF. Each OSPFv2 instance can
support multiple VRFs, up to the system limit. For more information, see
3 Virtualization."
Licensing Requirements for OSPFv2
The following table shows the licensing requirements for this feature:
Partial SPF for Network (type 2) LSAs, Network Summary (type 3) LSAs, and AS External (type
5) LSAs—When there is a change on any of these LSAs, Cisco NX-OS performs a faster partial
calculation rather than running the whole SPF calculation.
SPF timers—You can configure different timers for controlling SPF calculations. These timers
include exponential backoff for subsequent SPF calculations. The exponential backoff limits the
CPU load of multiple SPF calculations.
Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, NX-OS Release 5.0(3)U1(1)
Licensing Requirements for OSPFv2
Chapter 9, "Configuring Layer
3-11
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