512k routes

Some ISPs have started to report that their IPv4 routing tables now exceed 512k individual routes. At present we’re only seeing 502k routes but we’re nearly there.

Now for us this isn’t going to make any difference, our routers can all easily handle the routing table of this size, and the full IPv6 routing table of 30k routes all at the same time. However, it may start to affect things within other ISPs that we connect to. The likely things that we’ll see happening are,

• Some ISPs will just drop some IPv4 routes, or cease processing updates, which means gradually odd bits of the internet will cease to work.
• Some ISPs may fall into a software routing mode reducing in reduced performance.
• Some ISPs will rely on filtering to reduce the routing table in size by aggregating routes together.
• Some ISPs will alter their configuration for Cisco CAT6500 routers and disable IPv6 in order to increase the memory available in their routers for IPv4.

So watch out for oddities, and expect them to occur more and more frequently as the growth in the routing table gradually reveals which ISPs are running into trouble having not planned ahead.