We all knew it was coming. As more and more networks are created and the IP address space is subdivided more and more the global routing table that backbone routers have to store in memory grow.

Many older routers only have 512K of memory. If the size of the table exceeds that, the routers start dropping routes. Result: network outages.

That happened Tuesday morning at about 5 AM Eastern Standard Time (GMT-5).  Several ISP reported issues. Check here for current size of the GRT (Global Routing Table).

No malice is apparent.

Barrett Lyon, founder of several companies that used large swaths of networks such as Prolexic, BitGravity, 3Crowd and defense.net, and now Principal Strategist at F5 Networks said: “It was inevitable but what’s going to happen when IPv6 peaks past 20M routes?”

In other words this is only the beginning.

But it is not a catastrophe. Lyon states: “ There are a lot of things people can do to reduce the table… even if the hardware can’t do the full table there are ways to compress it. Not all routers need the full table, so it’s possible to get a partial table. You just have less resolution to control each specific route but that’s not always required in every situation.”

Look for more outages as network operators scramble to fix their tables or upgrade their gear.

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