Static IP allocation schemes for end users (commercial)

Graham Johnston johnstong at westmancom.com
Fri May 5 14:57:41 UTC 2017


I work for a cable MSO, meaning that our access network is DOCSIS based. 15 years ago when we had way more IP addresses than customers we had a static IP allocation scheme wherein we aligned a /24 with each node and reserved the first 20 or so IPs for static assignment, the rest being left for dynamic assignment. The primary reason behind this scheme was that as the network grew and a node moved from one CMTS to another we could pull the /24 with it and customers wouldn't have to re-address.

As our network has grown, in terms of the number of nodes, as well as the number of IPs in use we've come to the obvious conclusion that the old scheme isn't workable into the future. For instance I will soon have more nodes in service than I have /24s allocated to me.

Instead we are entertaining two basic options as an alternative.

  *   Create static reservations, as required, within the otherwise dynamic range.
     *   Whether or not the customer continues to DHCP or assigns the IP statically doesn't matter to me.
  *   Move to having a single subnet, or portion therein, per CMTS. This keeps the process more or less identical to what we do now.

Both of the schemes above would require the customer to undergo addressing changes in the event that we move their node between CMTSs in the future.

Can anyone else share what they are doing or otherwise identify if there is a best practice in this area?

Thanks,
Graham


More information about the NANOG mailing list