Small IX IP Blocks

Will Hargrave will at
Sun Apr 5 15:39:37 UTC 2015

On 5 Apr 2015, at 04:29, Paul Stewart <paul at> wrote:

> I worked for a provider until recently that happened to get an IP assignment
> at an IXP that was transitioning from /25 to /24.  It was painful chasing
> down peers to get them to change their netmask just so we could connect.
> This went on for several months dealing with the peering/network contacts of
> whom many of them didn't know the mask had changed in the first place.

If you had problems peering because other participants have the wrong netmask, the IXP is not being operated correctly. It’s such a very bad thing to have the incorrect netmask on interfaces (think, more-specifics, route leaks, etc) that the IXP should manage the netmask change process itself - in fact to the point of disconnecting networks who do not configure it correctly.

When we renumbered LONAP from /24 to /22, we had to change netblocks too. I can’t recall if we had any netmask problems too but it seems perfectly possible if lazy people just went %s/193.203.5/5.57.80/g. So we did check for that - it’s quite a simple task.

From an IXP user point of view, the change was easier for J users, but we built a config validator/renumbererer for C IOS users to help them out. (‘paste your config in this webform’ ‘examine the output’ sort of thing)


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