OSPF and IS-IS: Choosing an IGP for Large-Scale Networks

13.1. OSPF Extensions for Multi-Topology Routing

At the time of writing of this chapter, the first Internet Draft proposing Multi-Topology OSPF (MT-OSPF)^[1] is only a few months old, and MT-OSPF has not yet seen general deployment. By the time you read this, the extensions are likely to be on vendors’ development roadmaps, if not in production code.

^[1] Peter Psenak, Sina Mirtorabi, Abhay Roy, Liem Nguyen, and Padma Pillay-Esnault, “MT-OSPF: Multi-Topology (MT) Routing in OSPF,” draft-ietf-ospf-mt-00.txt, October 2004.

Although some extensions to OSPF have required new LSAs or even a new version of the protocol, MT-OSPF support is implemented simply by exploiting unused fields in modern OSPF LSAs. You might recall from Chapter 5 that OSPF was ...