OSPF RFC 1583 Compatibility
RFC 1583 is an early version of OSPFv2.
During OSPF external route calculations, routing loops may occur because RFC 2328 and RFC 1583 define different route selection rules. To prevent routing loops, both communication ends must use the same route selection rules. The mechanism is as follows:
- When RFC 1583 compatibility is enabled, OSPF uses route selection rules defined in RFC 1583.
- When RFC 1583 compatibility is disabled, OSPF uses route selection rules defined in RFC 2328.
OSPF calculates external routes using Type 5 LSAs. If the router with RFC 1583 compatibility enabled receives a Type 5 LSA:
- The router selects a route to the ASBR that originates the LSA or to the forwarding address (FA) described in the LSA.
- The router selects external routes to the same destination.
By default, OSPF uses route selection rules defined in RFC 1583.