Chapter 10. Keeping Your IPv6 Addresses Reachable

A name indicates what we seek. An address indicates where it is. A route indicates how we get there.

— Jon Postel


There wouldn’t be much point to the whole exercise of creating and managing a great IPv6 address plan if we didn’t also implement policies and practices that keep those addresses reachable.

Routing on our internal networks and across the Internet requires some considerations unique to IPv6. We’ll review the IPv6 versions of the routing protocols familiar to us from IPv4 with special attention to the differences that will help us keep our IPv6 addresses live.

Many enterprises (especially small to medium-sized organizations) have traditionally relied on PA IPv4 space from an ISP. They may be opting for an IPv6 PI allocation directly from a RIR for the first time. The practices to keep those IPv6 prefixes externally reachable and optimally routed may be less familiar to them.

We’ll also examine the impact of IPv6 routing table size on memory that may affect the overall reachability of our networks.

Routing with IPv6

Just as with IPv4, you’ll be relying on a routing protocol to get traffic between sites or within sites. Thankfully, for the sake of preserving our copious amounts of free time (CAFT), we don’t have to learn any new routing protocols exclusive to IPv6. That is, the IGPs and EGPs we know and (as long as we’ve configured them correctly and they’re behaving) love from IPv4 have all been ...

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