By default, the JUNOS implementation of OSPFv2 is compatible with RFC 1583, OSPF Version 2. This means that the JUNOS Software maintains a single best route to an AS boundary router in the OSPF routing table, rather than multiple intra-AS paths, if they are available. You can now disable compatibility with RFC 1583. It is preferable to do so when the same external destination is advertised by AS boundary routers that belong to different OSPF areas. When you disable compatibility with RFC 1583, the OSPF routing table maintains the multiple intra-AS paths that are available, which the router uses to calculate AS external routes as defined in RFC 2328, OSPF Version 2. Being able to use multiple, available paths to calculate an AS external route can prevent routing loops.
To disable OSPF v2 compatibility with RFC 1583, include the no-rfc-1583 statement:
For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.