OSPFv2
- OSPFv2 overview
- Autonomous System
- OSPFv2 components and roles
- Reduction of equivalent AS external LSAs
- Algorithm for AS external LSA reduction
- Enabling OSPFv2
A number of steps are required when enabling OSPFv2 on a device. - Backbone area
The backbone area (also known as area 0 or area 0.0.0.0) forms the core of OSPF networks. All other areas should be connected to the backbone area either by a direct link or by virtual link configuration. Routers that have interfaces in both backbone area and (at least one) non-backbone area are called Area Border Routers (ABR). Inter area routing happens via ABRs. - Assigning OSPFv2 areas
Areas can be assigned as OSPFv2 areas. - Area range
You can further consolidate routes at an area boundary by defining an area range. The area range allows you to assign an aggregate address to a range of IP and IPv6 addresses. - Area types
- Stub area and totally stubby area
A stub area is an area in which advertisements of external routes are not allowed, reducing the size of the database. A totally stubby area (TSA) is a stub area in which summary link-state advertisement (type 3 LSAs) are not sent. A default summary LSA, with a prefix of 0.0.0.0/0 is originated into the stub area by an ABR, so that devices in the area can forward all traffic for which a specific route is not known, via ABR. - Not-so-stubby area (NSSA)
- Assigning interfaces to an area
Once you define OSPFv2 areas, you can assign interfaces to the areas. All device ports must be assigned to one of the defined areas on an OSPFv2 device. When a port is assigned to an area, all corresponding subnets on that port are automatically included in the assignment. - Link state advertisements
- Virtual links
- Default route origination
When the device is an OSPFv2 Autonomous System Boundary Router (ASBR), you can configure it to automatically generate a default external route into an OSPFv2 routing domain. - External route summarization
An ASBR can be configured to advertise one external route as an aggregate for all redistributed routes that are covered by a specified address range. - SPF timers
The device uses an SPF delay timer and an SPF hold-time timer to calculate the shortest path for OSPFv2 routes. The values for both timers can be changed. - Modifying Shortest Path First timers
The Shortest Path First (SPF) throttle timers can be modified. - OSPFv2 LSA refreshes
To prevent a refresh from being performed each time an individual LSA's refresh timer expires, OSPFv2 LSA refreshes are delayed for a specified time interval. This pacing interval can be altered. - Support for OSPF RFC 2328 Appendix E
- OSPFv2 graceful restart
The graceful restart (GR) feature provides a routing device with the capability to inform its neighbors when it is performing a restart. - OSPFv2 stub router advertisement
- OSPFv2 Shortest Path First throttling
- IETF RFC and internet draft support
- OSPFv2 non-stop routing
OSPFv2 can continue operation without interruption during hitless failover when the OSPFv2 non-stop routing (NSR) feature is enabled. - Synchronization of critical OSPFv2 elements
- Standby module operations
- OSPFv2 distribute list
- OSPFv2 route redistribution
- Redistributing routes into OSPFv2
OSPFv2 routes can be redistributed, and the routes to be redistributed can be specified. - Load sharing
- Interface types to which the reference bandwidth does not apply
- Changing the reference bandwidth for the cost on OSPFv2 interfaces
- OSPFv2 over VRF
- Configuring the OSPFv2 Max-Metric Router LSA
By configuring the OSPFv2 max-metric router LSA you can enable OSPFv2 to advertise its locally generated router LSAs with a maximum metric. - Re-enabling OSPFv2 compatibility with RFC 1583
OSPFv2 is compatible with RFC 1583 and maintains a single best route to an autonomous system (AS) boundary router in the OSPF routing table. Disabling this compatibility causes the OSPF routing table to maintain multiple intra-AS paths, which helps prevent routing loops. You can re-enable OSPFv2 compatibility with RFC 1583 if it has been disabled. - Changing default settings
- Disabling and re-enabling OSPFv2 event logging
OSPFv2 event logging can be configured, disabled, and re-enabled. - Understanding the effects of disabling OSPFv2
- Disabling OSPFv2