How to manage Static IPs to customers

Aaron Gould aaron1 at
Fri May 8 19:34:57 UTC 2020

We have a provisioning system (promptlink) that we use to map cable modems
to their static ip addresses.  The provisioning system has a gui front end
and it sits on linux and also acts as a dhcp server, etc.  This is the same
ip address that we use for cable-helper (like ip-helper on a cmts bundle ip
interface) to forward dhcp requests from cable modem cpe, via the cmts, and
unicasted to promptlink and then the static ip address reservation within
the promptlink is sent back to the cpe

This all continues to work, even during node splits, as long as we don't
move that cm cpe to a different cmts... which would rarely happen since it's
across town to get to our other RF environment served be a different cmts
using a different static ip subnet... since we don't do L2 via cmts's in
order to stitch back that ip into a more globally located static subnet...
again, we don't do that.  If the customers moves locations, into a different
cmts area, that would be required to give back the single static /32 ip and
get a different on.  Unless they were a multi-static customer buying like a
/29... in which case we have no problem moving that /29 subnet off that cmts
and onto another one.  That's easy.

We do however have more centrally located subnets for some of our single
static ip customers in FTTH... but not CMTS docsis.


-----Original Message-----
From: NANOG [mailto:nanog-bounces at] On Behalf Of Javier Gutierrez
Sent: Thursday, May 7, 2020 3:50 PM
To: nanog at
Subject: How to manage Static IPs to customers

Hi there, 
Just wanted to reach out and get an idea how is people managing customers
with static Ips, more specifically on Docsis networks where the customer
could be moved between cmts's when a node is split

Thanks in advance for all responses,

Javier Gutierrez Guerra


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