OSPF/BGP Redistribution

Each of routing protocols OSPF and BGP may be enabled independently and the prior model of allowing only one routing protocol to be enabled on the system has been removed with this release. This release also allows the possibility of redistributing OSPF into BGP or BGP into OSPF (or both simultaneously), along with other possible route sources like prefixes learnt over the overlay, connected routes, static routes, etc.

In addition, with release 3.2, we are standardizing the redistribution behavior along more traditional lines (similar to that in other routing vendors). For example, if there is more than one route available for the same prefix, then only the best route for that prefix in the system RIB will be redistributed to the destination protocol if the configuration in the destination protocol allows redistribution for that route type.

Consider, as an example, redistribution of the prefix 192.168.1.0/24 into BGP. Let's say routes to the prefix 192.168.1.0/24 are locally available, learned from OSPF and separately learned as an Overlay prefix. Let's further assume that between the OFC flow ordering for the prefix, and route metrics, and route preference the OSPF route ranks above (is better than) the learned overlay route for that same prefix. Then, the OSPF route will be redistributed into BGP if OSPF redistribution has been turned on in BGP. Note that since the overlay learned prefix is not the best route for that prefix in the system RIB, it will not be redistributed into BGP even if the redistribution of overlay prefixes has been turned on in BGP.

In cases like the above, in order to facilitate the redistribution of the best route for a prefix into a given destination protocol, the user can enable redistribution for the specific route type that is the best route in the system.

Alternately, if the user prefers a different route source for that prefix to be redistributed into the destination protocol, the user can control the relative precedence of the route in the system RIB using the Overlay Flow Control facility provided by the management interface, or by varying the route metric.

See Enable OSPF and Enable BGP for more information.