The sheer physical size of an IPv6 address, along with its new notation, can make the transition from IPv4 a complex task. Further complicating this transition is the fact that there is more than one type of IPv6 routing configuration to choose from. A number of different feature topologies are available, and no matter which one you select, each autonomous system (AS), will have its own interior gateway protocol (IGP) technology. While issues related to AS will differ between service providers, the selection of a primary IGP core routing platform will be a fundamental decision in your transition to IPv6. The two most common platforms are OSPFv3 and IS-IS, and the factors that may affect your decision between the two are outlined below:
With its larger set of extensions and features, OSPFv3 is suited to the functional enhancements and topological flexibilities built into IPv6. The routing platform can quickly adjust to link failures and other changes by converging on new routing structures within seconds. It can also construct route tables based on link cost factors associated with each routing interface. Currently, OSPFv3 is widely used by enterprise networks.
Intermediate System to Intermediate System (IS-IS) offers greater scalability and can accommodate more routers in a given area. IS-IS has the ability of working in both the IPv4 and IPv6 domains (dual-stack mode), with dual functionality made possible through the introduction of multi-topology. This is an advantage over OSPFv2 and OSPFv3, which are limited to IPv4 and IPv6 respectively.
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