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Comment by pilif | Hacker News Reader

>The 512,000 route limitation can be increased to a higher number, for details see this Cisco doc

and that doc goes ahead to explain how to increase the limit at the cost of space for IPv6. Worse: The sample code (which everybody is going to paste) doubles the space for IPv4 at the cost of nearly all the IPv6 space, even though we should soon cross the threshold when we're going to see more IPv6 growth than IPv4 growth.

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There are only 18k IPv6 routes at the moment so the 256k in the default CAM allocation is way too much. In fact you could argue that this whole incident was made worse by Cisco believing people when they said v6 was going to take off, and wasting a bunch of memory on it.

Is there a better workaround that doesn't hinder IPv6?

I agree that it would be better not to harm IPv6 growth. But if the alternative is to break the IPv4 internet then the choice seems obvious.

The default sample code (which everybody is going to copy without reading about the consequences) could only slightly increase the V4 space instead of doubling it which we'll hopefully never need as V6 is going to grow much more quickly now (again: hopefully)

It does not harm IPv6 growth. Even years from now IPv4 will be larger than IPv6. IPv6 routes are huge so even just taking a small chunk of that allocated space for IPv4 will help.

I'd presume that the best workaround would be to begin replacing the older Cisco kit with newer models.

That's not a workaround - but yes, these things need to be upgraded. They're probably unmaintained anyway since good networking departments don't want to be working with super old gear.

Yes it's the solution rather than a workaround - my very British, dry sense of humour, at work there.

Although it could be argued that "workaround" is a sub-set of "solution" ;)

So, we go back to Verizon not upgrading and maintaining their network? (a la net neutrality debate vs. Level3)[1]

[1] http://blog.level3.com/global-connectivity/verizons-accident...

Who said it's Verizon running the old Cisco routers?

The OP's article (Verizon probably wasn't alone):

> So whatever happened internally at Verizon caused aggregation for these prefixes to fail which resulted in the introduction of thousands of new /24 routes into the global routing table. This caused the routing table to temporarily reach 515,000 prefixes and that caused issues for older Cisco routers.

Verizon might very well be running current hardware. They have announced too many routes which in turn let the global table grow too big which was causing problems with routers all over the place.

The connectivity issue was caused by the routing table to grow too big for old routers used all over the place.

The routing table grew too big because of a mistake by Verizon which might or might not have been running old routers.

It might not have even been Verizon's mistake. When you peer with an ISP it is the customer's router that announces the routes. Announcing all of your networks individually is literally a one line change in most router configs so it's an easy mistake to make. If the ISP is being defensive, and good ones are, they filter incoming routes to make sure they belong to the customer. But they may not have a filter that mandates that they're aggregated since that usually isn't a problem.

And where does that say Verizon is old Cisco routers?

"which everybody is going to paste"

I question the assertion that many people in charge of Cisco routers doing BGP are in the habit of pasting in configuration changes without thinking about them.

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