We're going to use this section to look at how to migrate from OSPF to IS-IS. We have been through the process of making the decision about which protocol we should be using, and we may have OSPF already deployed on our network, and we've decided that maybe IS-IS is the way we want to go for the future. So how do we do it? It's actually not as difficult as it first might seem. Certainly with the advent of IPv6 and dual stack networks, more and more network operators are expressing an interest to move over to using IS-IS. The presentation is going to describe the process and is based on several successful migrations that colleagues have performed over the last decade or so. We'll show you configuration examples using Cisco IOS and Cisco IOS XR. We've covered previously about the motivations that IS-IS runs in the data link layer is perceived to be more secure than using OSPF which runs on top of IP. We've seen that IS-IS is not dependent on IP addressing, and the perception that IS-IS has been used for so long by so many of the world's biggest network operators. But that some how the equipment vendors would probably be paying more attention to IS-IS's reliability, scalability, and features than they would do with OSPF, and also the migration to IPv6. Adding IPv6 to our network means OSPFv2 and OSPFv3 are required in the network. Two protocols with two sets of identical configuration to handle IPv4 and IPv6. While there is RFC5838 to describe support of multiple address families in OSPFv3, there's limited vendor support, and it's not compatible with OSPFv2 either. For IS-IS we simply add the v6 address-family. Most networks today are operating single topology to handle both v4 and v6 prefixes. Newer networks deploying v6 for the first time will often operate IS-IS with multi-topology, which allows them to do an incremental deployment of IPv6.

© Produced by Philip Smith and the Network Startup Resource Center, through the University of Oregon.

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