Virtual aggregation can manage internet routing tables

Ivan Pepelnjak
25 Aug 2010

Internet routing tables are multiplying, which means IPv4 address depletion will only make matters worse by introducing lots of shorter IPv4 prefixes generated by service providers buying and selling chunks of IPv4 address space.

Introducing IPv6 will only exacerbate the problem since it doesn't address the needs of multihomed sites, and we will have to live with the transition of running IPv4 and IPv6 concurrently for years, if not decades.

Another sobering note is that the Internet Engineering Task Force (IETF) recognized in 2007 that routing scalability was the most important problem facing the Internet -- and it still is.

Virtual aggregation technology offers a solution that can reduce the size of the forwarding table on a carrier edge router by a factor of 10 to 20 (see Making Routers Last Longer with ViAggre), extending the usable lifetime of these boxes for up to a decade.

When you try to evaluate the impact of exploding Border Gateway Protocol (BGP) tables and IP routing tables on your network, it's important to keep in mind the multi-layer structure of BGP, IP and forwarding tables implemented in most modern routers. Here's why:

BGP tables store all viable information received from BGP neighbors. Each IP prefix reachable in the Internet might have numerous entries in the BGP table, as it could be advertised by several BGP peers. For example, Hurricane Electric receives more than 10 different prefixes for Facebook's IP prefix on its Fremont core router.

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