+1 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. Paul -----Original Message----- From: NANOG [mailto:nanog-bounces@nanog.org] On Behalf Of Bill Woodcock Sent: Saturday, April 4, 2015 10:36 PM To: Mike Hammett Cc: NANOG list Subject: Re: Small IX IP Blocks
On Apr 4, 2015, at 7:28 PM, Charles Gucker <cgucker@onesc.net> wrote:
I've been involved in IX renumbering efforts because exchange(s) decided to use /25's instead of /24's. It's painful because troubleshooting can be a little difficult as differing subnetmasks are in play. If you have the address space, use a /24. ARIN has IPv4 address space specifically reserved for the use by IXPs.
Yes. Listen to Charlie. We did a bunch of analysis on size of IXP subnets, and how it changes over time, relative to the age of the IXP. To summarize drastically, the first /24 typically lasts about 15-18 years. Only a tiny handful of exchanges (less than 2%) are actually supporting more than 254 participants yet at this point. That number will continue to grow over time. At the same time, it's not worth the trouble of renumbering more than once in that time period, so don't be penny-wise and pound-foolish by trying to use a /25, particularly when ARIN hands out /24s to IXPs specifically to keep them from running into that trap. -Bill