- Configuring OSPF
- OSPF Stub Router Advertisement
- OSPF Update Packet-Pacing Configurable Timers
- OSPF Sham-Link Support for MPLS VPN
- OSPF Support for Multi-VRF on CE Routers
- OSPF Forwarding Address Suppression in Translated Type-5 LSAs
- OSPF Inbound Filtering Using Route Maps with a Distribute List
- OSPF Shortest Path First Throttling
- OSPF Support for Fast Hello Packets
- OSPF Incremental SPF
- OSPF Limit on Number of Redistributed Routes
- OSPF Link-State Advertisement Throttling
- OSPF Support for Unlimited Software VRFs per PE Router
- OSPF Area Transit Capability
- OSPF Per-Interface Link-Local Signaling
- OSPF Link-State Database Overload Protection
- OSPF MIB Support of RFC 1850 and Latest Extensions
- OSPF Enhanced Traffic Statistics
- Configuring OSPF TTL Security Check and OSPF Graceful Shutdown
- OSPF Sham-Link MIB Support
- OSPF SNMP ifIndex Value for Interface ID in Data Fields
- OSPFv2 Local RIB
- OSPF Support for Forwarding Adjacencies over MPLS TE Tunnels
- Enabling OSPFv2 on an Interface Basis
- OSPF NSR
- OSPFv2 Loop-Free Alternate Fast Reroute
OSPF NSR
The OSPF NSR feature allows a router with redundant Route Processors (RPs)to maintain its Open Shortest Path First (OSPF) state and adjacencies across planned and unplanned RP switchovers. It does this by checkpointing state information from OSPF on the active RP to the standby RP. Later, following a switchover to the standby RP, OSPF can use this checkpointed information to continue operation without interruption.
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for OSPF NSR
- OSPF NSR is available for platforms with redundant RPs or Cisco IOS software redundancy running Cisco IOS Release XE 3.3S or later releases.
Restrictions for OSPF NSR
- OSPF nonstop routing (NSR) can significantly increase the memory used by OSPF during certain phases of its operation. CPU usage also can be increased. You should be aware of router memory capacity and estimate the likely memory requirements of OSPF NSR. For more information see Configuring OSPF NSR. For routers where memory and CPU are constrained you might want to consider using OSPF NSF instead. For more information, see OSPF RFC 3623 Graceful Restart Helper Mode.
- A switchover from the active to the standby RP can take several seconds, depending on the hardware platform, and during this time OSPF is unable to send Hello packets. As a result, configurations that use small OSPF dead intervals might not be able to maintain adjacencies across a switchover.
Information About OSPF NSR
OSPF NSR Functionality
Although OSPF NSR serves a similar function to OSPF NSF, it works differently. With NSF, OSPF on the newly active standby RP initially has no state information, so it uses extensions to the OSPF protocol to recover its state from neighboring OSPF routers. For this to work, the neighbors must support the NSF protocol extensions and be willing to act as "helpers" to the restarting router. They must also continue forwarding data traffic to the restarting router while this recovery is taking place.
With NSR, by contrast, the router performing the switchover preserves its state internally, and in most cases the neighbors are unaware that anything has happened. Because no assistance is needed from neighboring routers, NSR can be used in situations where NSF cannot; for example, in networks where not all the neighbors implement the NSF protocol extensions, or where network topology changes during the recovery can make NSF unreliable.
How to Configure OSPF NSR
Configuring OSPF NSR
Perform this task to configure OSPF NSR.
NSR adds a single new line, "nsr," to the OSPF router mode configuration. Routers that do not support NSR, for whatever reason, will not accept this command.
 Note |
> |
DETAILED STEPS
Troubleshooting Tips
OSPF NSR can increase the amount of memory used by the OSPF router process. To determine how much memory OSPF is currently using without NSR you can use the show processes and show processes memory commands:
Router# show processes | include OSPF 276 Mwe 133BE14 1900 1792 1060 8904/12000 0 OSPF-1 Router 296 Mwe 133A824 10 971 10 8640/12000 0 OSPF-1 Hello
Process 276 is the OSPF router process that is to be checked. The show processes memory command is used to display its current memory use:
Router# show processes memory 276 Process ID: 276 Process Name: OSPF-1 Router Total Memory Held: 4454800 bytes
In this case OSPF is using 4,454,800 bytes or approximately 4.5 megabytes (MB). OSPF NSR could double this for brief periods, so you should make sure the router has at least 5 MB of free memory before enabling OSPF NSR.
Configuration Examples for OSPF NSR
Example Configuring OSPF NSR
The following example shows how to configure OSPF NSR:
router> enable Router# configure terminal Router(config)# router ospf 1 Router(config-router)# nsr Router(config-router)# end Router# show ip ospf 1 nsr Standby RP Operating in duplex mode Redundancy state: STANDBY HOT Peer redundancy state: ACTIVE ISSU negotation complete ISSU versions compatible Routing Process "ospf 1" with ID 10.1.1.100 NSR configured Checkpoint message sequence number: 3290 Standby synchronization state: synchronized Bulk sync operations: 1 Last sync start time: 15:22:48.971 UTC Fri Jan 14 2011 Last sync finish time: 15:22:48.971 UTC Fri Jan 14 2011 Last sync lost time: - Last sync reset time: - LSA Count: 2, Checksum Sum 0x00008AB4
The output shows that OSPF NSR is configured and that OSPF on the standby RP is fully synchronized and ready to continue operation should the active RP fail or if a manual switchover is performed.
Additional References
Related Documents
| Related Topic |
Document Title |
|---|---|
| Cisco IOS commands |
|
| OSPF commands |
Cisco IOS IP Routing: OSPF Command Reference |
| Configuring IETF NSF or Cisco NSF |
NSF--OSPF (RFC 3623 OSPF Graceful Restart) |
Standards
| Standard |
Title |
|---|---|
| None |
-- |
MIBs
| MIB |
MIBs Link |
|---|---|
| None |
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
| RFC |
Title |
|---|---|
| RFC 2328 |
OSPF Version 2 |
Technical Assistance
| Description |
Link |
|---|---|
| The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for OSPF NSR
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
| Table 1 | Feature Information for OSPF NSR |
| Feature Name |
Releases |
Feature Information |
|---|---|---|
| OSPF NSR |
XE 3.3S |
The OSPF NSR feature allows a router with redundant route processors to maintain its OSPF state and adjacencies across planned and unplanned RP switchovers. In Cisco IOS Release XE 3.3S, this feature was introduced. The following commands were introduced or modified: nsr, show ip ospf nsr. |
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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