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Cisco IOS XE IPv6 Configuration Guide, Release 2
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Start Here: Cisco IOS XE Software Release Specifics for IPv6 Features
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Implementing IPv6 Addressing and Basic Connectivity
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Implementing ADSL and Deploying Dial Access for IPv6
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Implementing Bidirectional Forwarding Detection for IPv6
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Implementing DHCP for IPv6
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Implementing EIGRP for IPv6
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Implementing IS-IS for IPv6
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Implementing IPv6 for Network Management
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Implementing Multiprotocol BGP for IPv6
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Implementing IPv6 Multicast
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Implementing OSPF for IPv6
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Implementing QoS for IPv6
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Implementing RIP for IPv6
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Implementing Traffic Filters and Firewalls for IPv6 Security
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Implementing Static Routes for IPv6
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Implementing Tunneling for IPv6
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Implementing IPsec in IPv6 Security
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Table Of Contents
Prerequisites for Implementing OSPF for IPv6
Restrictions for Implementing OSPF for IPv6
Information About Implementing OSPF for IPv6
Comparison of OSPF for IPv6 and OSPF Version 2
Fast Convergence—LSA and SPF Throttling
Addresses Imported into OSPF for IPv6
Link Quality Metrics Reporting for OSPFv3 with VMI Interfaces
How to Implement OSPF for IPv6
Enabling OSPF for IPv6 on an Interface
Defining an OSPF for IPv6 Area Range
Configuring LSA and SPF Throttling for OSPF for IPv6 Fast Convergence
Enabling Event Logging for LSA and SPF Rate Limiting
Clearing the Content of an Event Log
Enabling OSPFv3 Graceful Restart
Enabling OSPFv3 Graceful Restart on a Graceful-Restart-Capable Router
Enabling OSPFv3 Graceful Restart on a Graceful-Restart-Aware Router
Verifying OSPF for IPv6 Configuration and Operation
Configuration Examples for Implementing OSPF for IPv6
Enabling OSPF for IPv6 on an Interface Configuration: Example
Defining an OSPF for IPv6 Area Range: Example
Configuring LSA and SPF Throttling for OSPF for IPv6 Fast Convergence: Example
Forcing SPF Configuration: Example
Feature Information for Implementing OSPF for IPv6
Implementing OSPF for IPv6
First Published: March 17, 2003Last Updated: March 2, 2009This module expands on Open Shortest Path First (OSPF) to provide support for IPv6 routing prefixes. This module describes the concepts and tasks you need to implement OSPF for IPv6 on your network.
Finding Feature Information
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 for Implementing OSPF for IPv6" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS XE software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
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Prerequisites for Implementing OSPF for IPv6
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Prerequisites for Implementing OSPF for IPv6
Before you enable OSPF for IPv6 on an interface, you must do the following:
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This document assumes that you are familiar with IPv4. Refer to the publications referenced in the "Related Documents" section for IPv4 configuration and command reference information.
Restrictions for Implementing OSPF for IPv6
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Information About Implementing OSPF for IPv6
To implement OSPF for IPv6, you need to understand the following concepts:
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How OSPF for IPv6 Works
OSPF is a routing protocol for IP. It is a link-state protocol, as opposed to a distance-vector protocol. Think of a link as being an interface on a networking device. A link-state protocol makes its routing decisions based on the states of the links that connect source and destination machines. The state of a link is a description of that interface and its relationship to its neighboring networking devices. The interface information includes the IPv6 prefix of the interface, the network mask, the type of network it is connected to, the routers connected to that network, and so on. This information is propagated in various type of link-state advertisements (LSAs).
A router's collection of LSA data is stored in a link-state database. The contents of the database, when subjected to the Dijkstra algorithm, result in the creation of the OSPF routing table. The difference between the database and the routing table is that the database contains a complete collection of raw data; the routing table contains a list of shortest paths to known destinations via specific router interface ports.
OSPF version 3, which is described in RFC 2740, supports IPv6.
Comparison of OSPF for IPv6 and OSPF Version 2
Much of the OSPF for IPv6 feature is the same as in OSPF version 2. OSPF version 3 for IPv6, which is described in RFC 2740, expands on OSPF version 2 to provide support for IPv6 routing prefixes and the larger size of IPv6 addresses.
In OSPF for IPv6, a routing process does not need to be explicitly created. Enabling OSPF for IPv6 on an interface will cause a routing process, and its associated configuration, to be created.
In OSPF for IPv6, each interface must be enabled using commands in interface configuration mode. This feature is different from OSPF version 2, in which interfaces are indirectly enabled using the router configuration mode.
In IPv6, users can configure many address prefixes on an interface. In OSPF for IPv6, all address prefixes on an interface are included by default. Users cannot select some address prefixes to be imported into OSPF for IPv6; either all address prefixes on an interface are imported, or no address prefixes on an interface are imported.
Unlike OSPF version 2, multiple instances of OSPF for IPv6 can be run on a link.
In OSPF for IPv6, it is possible that no IPv4 addresses will be configured on any interface. In this case, the user must use the router-id command to configure a router ID before the OSPF process will be started. A router ID is a 32-bit opaque number. OSPF version 2 takes advantage of the 32-bit IPv4 address to pick an IPv4 address as the router ID. If an IPv4 address does exist when OSPF for IPv6 is enabled on an interface, then that IPv4 address is used for the router ID. If more than one IPv4 address is available, a router ID is chosen using the same rules as for OSPF version 2.
OSPF automatically prefers a loopback interface over any other kind, and it chooses the highest IP address among all loopback interfaces. If no loopback interfaces are present, the highest IP address in the router is chosen. You cannot tell OSPF to use any particular interface.
LSA Types for IPv6
The following list describes LSA types, each of which has a different purpose:
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An address prefix occurs in almost all newly defined LSAs. The prefix is represented by three fields: PrefixLength, PrefixOptions, and Address Prefix. In OSPF for IPv6, addresses for these LSAs are expressed as prefix, prefix length instead of address, mask. The default route is expressed as a prefix with length 0. Type 3 and Type 9 LSAs carry all IPv6 prefix information that, in IPv4, is included in router LSAs and network LSAs. The Options field in certain LSAs (router LSAs, network LSAs, interarea-router LSAs, and link LSAs) has been expanded to 24 bits to provide support for OSPF in IPv6.
In OSPF for IPv6, the sole function of link-state ID in interarea-prefix LSAs, interarea-router LSAs, and autonomous-system external LSAs is to identify individual pieces of the link-state database. All addresses or router IDs that are expressed by the link-state ID in OSPF version 2 are carried in the body of the LSA in OSPF for IPv6.
The link-state ID in network LSAs and link LSAs is always the interface ID of the originating router on the link being described. For this reason, network LSAs and link LSAs are now the only LSAs whose size cannot be limited. A network LSA must list all routers connected to the link, and a link LSA must list all of the address prefixes of a router on the link.
Fast Convergence—LSA and SPF Throttling
The OSPF for IPv6 LSA and SPF throttling feature provides a dynamic mechanism to slow down link-state advertisement updates in OSPF during times of network instability. It also allows faster OSPF convergence by providing LSA rate limiting in milliseconds.
Previously, OSPF for IPv6 used static timers for rate-limiting SPF calculation and LSA generation. Although these timers are configurable, the values used are specified in seconds, which poses a limitation on OSPF for IPv6 convergence. LSA and SPF throttling achieves subsecond convergence by providing a more sophisticated SPF and LSA rate-limiting mechanism that is able to react quickly to changes and also provide stability and protection during prolonged periods of instability.
Addresses Imported into OSPF for IPv6
When importing the set of addresses specified on an interface on which OSPF for IPv6 is running into OSPF for IPv6, users cannot select specific addresses to be imported. Either all addresses are imported, or no addresses are imported.
OSPF for IPv6 Customization
You can customize OSPF for IPv6 for your network, but you likely will not need to do so. The defaults for OSPF in IPv6 are set to meet the requirements of most customers and features. If you must change the defaults, refer to the IPv6 command reference to find the appropriate syntax.
Caution
OSPF for IPv6 Virtual Links
For each virtual link, a master security information datablock is created for the virtual link. Because a secure socket must be opened on each interface, there will be a corresponding security information datablock for each interface in the transit area. The secure socket state is kept in the interface's security information datablock. The state field in the master security information datablock reflects the status of all of the secure sockets opened for the virtual link. If all of the secure sockets are UP, then the security state for the virtual link will be set to UP.
Link Quality Metrics Reporting for OSPFv3 with VMI Interfaces
OSPFv3 is one of the routing protocols that can be used with Virtual Multipoint Interfaces (VMIs) in router-to-radio networks. The quality of a radio link has a direct impact on the throughput that can be achieved by router-router traffic. The PPPoE protocol has been extended to provide a process by which a router can request, or a radio can report, link quality metric information. Cisco's OSFPv3 implementation has been enhanced so that the route cost to a neighbor is dynamically updated based on metrics reported by the radio, thus allowing the best route to be chosen within a given set of radio links.
The routing protocols receive raw radio link data, and compute a composite quality metric for each link. In computing these metrics, the following factors may be considered:
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Metrics can be weighted during the configuration process to emphasize or de-emphasize particular characteristics. For example, if throughput is a particular concern, the current data rate metric could be weighted so that it is factored more heavily into the composite metric. Similarly, a metric that is of no concern can be omitted from the composite calculation.
Link metrics can change rapidly, often by very small degrees, which could result in a flood of meaningless routing updates. In a worst case scenario, the network would be churning almost continuously as it struggled to react to minor variations in link quality. To alleviate this concern, Cisco provides a tunable dampening mechanism that allows the user to configure threshold values. Any metric change that falls below the threshold is ignored.The quality of a connection to a neighbor varies, based on various characteristics of the interface when OSPF is used as the routing protocol. The routing protocol receives dynamic raw radio link characteristics and computes a composite metric that is used to reduce the effect of frequent routing changes.
A tunable hysteresis mechanism allows users to adjust the threshold to the routing changes that occur when the router receives a signal that a new peer has been discovered, or that an existing peer is unreachable. The tunable metric is weighted and is adjusted dynamically to account for the following characteristics:
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Individual weights can be deconfigured and all weights can be cleared so that the cost is set back to the default value for the interface type. Based on the routing changes that occur, cost can be determined by the application of these metrics.
OSPFv3 Graceful Restart
The graceful restart feature in OSPFv3 allows nonstop data forwarding along routes that are already known while the OSPFv3 routing protocol information is being restored. A router can participate in graceful restart either in restart mode (such as in a graceful-restart-capable router) or in helper mode (such as in a graceful-restart-aware router).
To perform the graceful restart function, a router must be in high availability (HA) stateful switchover (SSO) mode (that is, dual RP). A router capable of graceful restart will perform the graceful restart function when the following failures occur:
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The graceful restart feature requires that neighboring routers be graceful-restart aware.
For further information about SSO and nonstop forwarding (NSF), see the Stateful Switchover and Cisco Nonstop Forwarding documents.
How to Implement OSPF for IPv6
This section contains the following procedures:
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Enabling OSPF for IPv6 on an Interface
This task explains how to enable OSPF for IPv6 routing and configure OSPF for IPv6 on each interface. By default, OSPF for IPv6 routing is disabled and OSPF for IPv6 is not configured on an interface.
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Defining an OSPF for IPv6 Area Range
The cost of the summarized routes will be the highest cost of the routes being summarized. For example, if the following routes are summarized:
OI 2001:0DB8:0:0:7::/64 [110/20]via FE80::A8BB:CCFF:FE00:6F00, gigabitethernet0/0/0OI 2001:0DB8:0:0:8::/64 [110/100]via FE80::A8BB:CCFF:FE00:6F00, gigabitethernet0/0/0OI 2001:0DB8:0:0:9::/64 [110/20]via FE80::A8BB:CCFF:FE00:6F00, gigabitethernet0/0/0They become one summarized route, as follows:
OI 2001:0DB8::/48 [110/100]via FE80::A8BB:CCFF:FE00:6F00, gigabitethernet0/0/0This task explains how to consolidate or summarize routes for an OSPF area.
Prerequisites
OSPF for IPv6 routing must be enabled.
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Configuring LSA and SPF Throttling for OSPF for IPv6 Fast Convergence
This task explains how to configure LSA and SPF throttling for the OSPF for IPv6 Fast Convergence feature.
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Enabling Event Logging for LSA and SPF Rate Limiting
An OSPF for IPv6 event log is kept for each OSPF for IPv6 instance. This task explains how to enable event logging for the LSA and SPF rate-limiting function.
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Clearing the Content of an Event Log
This task explains how to clear an event log.
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Enabling OSPFv3 Graceful Restart
The graceful restart feature may be enabled on graceful-restart-capable routers and on graceful-restart-aware routers. The following sections describe how to enable OSPFv3 graceful restart:
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Enabling OSPFv3 Graceful Restart on a Graceful-Restart-Capable Router
This task describes how to enable OSPFv3 graceful restart on a graceful-restart-capable router.
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Enabling OSPFv3 Graceful Restart on a Graceful-Restart-Aware Router
This task describes how to enable OSPFv3 graceful restart on a graceful-restart-aware router.
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Forcing an SPF Calculation
This task explains how to start the SPF algorithm without first clearing the OSPF database.
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Verifying OSPF for IPv6 Configuration and Operation
This task explains how to display information to verify the configuration and operation of OSPF for IPv6.
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Examples
This section provides the following output examples:
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Sample Output for the show ipv6 ospf interface Command
The following is sample output from the show ipv6 ospf interface command with regular interfaces and a virtual link that are protected by encryption and authentication:
Router# show ipv6 ospf interfaceOSPFv3_VL1 is up, line protocol is upInterface ID 69Area 0, Process ID 1, Instance ID 0, Router ID 10.0.0.1Network Type VIRTUAL_LINK, Cost: 64Configured as demand circuit.Run as demand circuit.DoNotAge LSA allowed.NULL encryption SHA-1 auth SPI 3944, secure socket UP (errors: 0)Transmit Delay is 1 sec, State POINT_TO_POINT,Timer intervals configured, Hello 2, Dead 10, Wait 40, Retransmit 5Hello due in 00:00:00Index 1/3/5, flood queue length 0Next 0x0(0)/0x0(0)/0x0(0)Last flood scan length is 1, maximum is 1Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 1, Adjacent neighbor count is 1Adjacent with neighbor 10.2.0.1 (Hello suppressed)Suppress hello for 1 neighbor(s)OSPFv3_VL0 is up, line protocol is upInterface ID 67Area 0, Process ID 1, Instance ID 0, Router ID 10.0.0.1Network Type VIRTUAL_LINK, Cost: 128Configured as demand circuit.Run as demand circuit.DoNotAge LSA allowed.MD5 authentication SPI 940, secure socket UP (errors: 0)Transmit Delay is 1 sec, State POINT_TO_POINT,Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:09Index 1/2/4, flood queue length 0Next 0x0(0)/0x0(0)/0x0(0)Last flood scan length is 1, maximum is 10Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 1, Adjacent neighbor count is 1Adjacent with neighbor 10.1.0.1 (Hello suppressed)Suppress hello for 1 neighbor(s)Gigabitethernet1/0/0 is up, line protocol is upLink Local Address FE80::A8BB:CCFF:FE00:6601, Interface ID 6Area 0, Process ID 1, Instance ID 0, Router ID 10.0.0.1Network Type BROADCAST, Cost: 10Transmit Delay is 1 sec, State DR, Priority 1Designated Router (ID) 10.0.0.1, local address FE80::A8BB:CCFF:FE00:6601No backup designated router on this networkTimer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:09Index 1/1/1, flood queue length 0Next 0x0(0)/0x0(0)/0x0(0)Last flood scan length is 0, maximum is 0Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 0, Adjacent neighbor count is 0Suppress hello for 0 neighbor(s)Serial12/0 is up, line protocol is upLink Local Address FE80::A8BB:CCFF:FE00:6600, Interface ID 50Area 1, Process ID 1, Instance ID 0, Router ID 10.0.0.1Network Type POINT_TO_POINT, Cost: 64AES-CBC encryption SHA-1 auth SPI 2503, secure socket UP (errors: 0)authentication NULLTransmit Delay is 1 sec, State POINT_TO_POINT,Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:09Index 1/2/3, flood queue length 0Next 0x0(0)/0x0(0)/0x0(0)Last flood scan length is 1, maximum is 5Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 1, Adjacent neighbor count is 1Adjacent with neighbor 10.2.0.1Suppress hello for 0 neighbor(s)Serial11/0 is up, line protocol is upLink Local Address FE80::A8BB:CCFF:FE00:6600, Interface ID 46Area 1, Process ID 1, Instance ID 0, Router ID 10.0.0.1Network Type POINT_TO_POINT, Cost: 64MD5 authentication (Area) SPI 500, secure socket UP (errors: 0)Transmit Delay is 1 sec, State POINT_TO_POINT,Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5Hello due in 00:00:09Index 1/1/2, flood queue length 0Next 0x0(0)/0x0(0)/0x0(0)Last flood scan length is 1, maximum is 5Last flood scan time is 0 msec, maximum is 0 msecNeighbor Count is 1, Adjacent neighbor count is 1Adjacent with neighbor 1.0.0.1Suppress hello for 0 neighbor(s)Sample Output for the show ipv6 ospf Command
The following is sample output from the show ipv6 ospf command:
Router# show ipv6 ospfRouting Process "ospfv3 1" with ID 172.16.3.3It is an autonomous system boundary routerRedistributing External Routes from,staticSPF schedule delay 5 secs, Hold time between two SPFs 10 secsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsLSA group pacing timer 240 secsInterface flood pacing timer 33 msecsRetransmission pacing timer 66 msecsNumber of external LSA 1. Checksum Sum 0x218DNumber of areas in this router is 1. 1 normal 0 stub 0 nssaArea 1Number of interfaces in this area is 2SPF algorithm executed 9 timesNumber of LSA 15. Checksum Sum 0x67581Number of DCbitless LSA 0Number of indication LSA 0Number of DoNotAge LSA 0Flood list length 0Sample Output for the show ipv6 ospf graceful-restart Command
The following is sample output from the show ipv6 ospf graceful-restart command:
Router# show ipv6 ospf graceful-restartRouting Process "ospf 1"Graceful Restart enabledrestart-interval limit: 120 sec, last restart 00:00:15 ago (took 36 secs)Graceful Restart helper support enabledRouter status : ActiveRouter is running in SSO modeOSPF restart state : NO_RESTARTRouter ID 10.1.1.1, checkpoint Router ID 10.0.0.0Configuration Examples for Implementing OSPF for IPv6
This section provides the following configuration examples:
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Enabling OSPF for IPv6 on an Interface Configuration: Example
The following example configures an OSPF routing process 109 to run on the interface and puts it in area 1:
ipv6 ospf 109 area 1Defining an OSPF for IPv6 Area Range: Example
The following example specifies an OSPF for IPv6 area range:
interface gigabitethernet7/0/0ipv6 address 2001:0DB8:0:0:7::/64 eui-64ipv6 enableipv6 ospf 1 area 1!interface gigabitethernet8/0/0ipv6 address 2001:0DB8:0:0:8::/64 eui-64ipv6 enableipv6 ospf 1 area 1!interface gigabitethernet9/0/0ipv6 address 2001:0DB8:0:0:9::/64 eui-64ipv6 enableipv6 ospf 1 area 1!ipv6 router ospf 1router-id 10.11.11.1area 1 range 2001:0DB8::/48Configuring LSA and SPF Throttling for OSPF for IPv6 Fast Convergence: Example
The following example displays the configuration values for SPF and LSA throttling timers:
Router# show ipv6 ospf
Routing Process "ospfv3 1" with ID 10.9.4.1
Event-log enabled, Maximum number of events: 1000, Mode: cyclic
It is an autonomous system boundary router
Redistributing External Routes from,
ospf 2
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
Forcing SPF Configuration: Example
The following example triggers SPF to redo the SPF and repopulate the routing tables:
clear ipv6 ospf force-spfAdditional References
The following sections provide additional references related to the Implementing OSPF for IPv6 feature.
Related Documents
Configuring a router ID in OSPF
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LSA throttling
"OSPF Link-State Advertisement (LSA) Throttling," Cisco IOS XE IP Routing Protocols Configuration Guide
OSPF for IPv6 commands
IPv6 supported feature list
"Start Here: Cisco IOS XE Software Release Specifics for IPv6 Features," Cisco IOS XE IPv6 Configuration Guide
Implementing basic IPv6 connectivity
"Implementing IPv6 Addressing and Basic Connectivity," Cisco IOS XE IPv6 Configuration Guide
Stateful switchover
"Stateful Switchover," Cisco IOS XE High Availability Configuration Guide
Cisco nonstop forwarding
"Cisco Nonstop Forwarding," Cisco IOS XE High Availability Configuration Guide
OSPF for IPv4 commands
Security configuration tasks (IPv4)
Cisco IOS XE Security Configuration Guide, Release 2
Security commands: complete command syntax, command mode, defaults, usage guidelines, and examples (IPv4)
Cisco IOS master command list, all releases
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
The draft RFC supported is as follows:
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Technical Assistance
Feature Information for Implementing OSPF for IPv6
Table 1 lists the features in this module and provides links to specific configuration information.
For information about a feature in this technology that is not documented here, see the Start Here: Cisco IOS XE Software Release Specifics for IPv6 Features.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note
Table 1 Feature Information for Implementing OSPF for IPv6
IPv6 routing: OSPF for IPv6 (OSPFv3)
Cisco IOS XE Release 2.1
OSPF version 3 for IPv6 expands on OSPF version 2 to provide support for IPv6 routing prefixes and the larger size of IPv6 addresses.
This entire document provides information about this feature.
The following commands were modified by this feature: area range, clear ipv6 ospf, ipv6 ospf area, ipv6 router ospf, show ipv6 ospf, show ipv6 ospf interface
IPv6 routing: LSA types in OSPF for IPv6
Cisco IOS XE Release 2.1
A router's collection of LSA data is stored in a link-state database. The contents of the database, when subjected to the Dijkstra algorithm, result in the creation of the OSPF routing table.
The following sections provide information about this feature:
IPv6 routing: Fast Convergence—LSA and SPF throttling
Cisco IOS XE Release 2.1
The OSPF for IPv6 LSA and SPF throttling feature provides a dynamic mechanism to slow down link-state advertisement updates in OSPF during times of network instability.
The following sections provide information about this feature:
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The following commands were modified by this feature: clear ipv6 ospf events, event-log, ipv6 router ospf, show ipv6 ospf event, timers lsa arrival, timers pacing flood, timers throttle lsa, timers throttle spf
OSPFv3 graceful restart
Cisco IOS XE Release 2.1
The graceful restart feature in OSPFv3 allows nonstop data forwarding along routes that are already known while the OSPFv3 routing protocol information is being restored.
The following sections provide information about this feature:
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The following commands were modified by this feature: graceful-restart, graceful-restart helper, ipv6 router ospf, show ipv6 ospf graceful-restart
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