atdma-tdma mixed mode questions |

You are here

atdma-tdma mixed mode questions

7 posts / 0 new
Last post
atdma-tdma mixed mode questions

We recently did a move to mixed mode on our cmts. Things went well in general, but there are several modems on the system that appear to be DOCSIS 2.0 capable, but show up registered as DOCSIS 1.0 (or 1.1). Here's an example from a "show cable modem docsis version":

0025.f176.xxxx C3/0/U1 online 814 1.1 1.0 tdma NB

We decided to use this modem to do some further testing, so we swapped it out and brought it into the office, thinking that it either needed a firmware upgrade, or that we could do some testing to figure out what else needed to be done to get all of the remaining modems to register as DOCSIS 2.0. However, once we got it back to the office and booted up, a subsequent "show cable modem docsis version" shows this modem as registering as DOCSIS 2.0. Logging into the modem reveals that it is indeed DOCSIS 2.0 capable. I have checked a couple of the other modems that are still showing up as DOCSIS 1.1 or 1.0 using snmpwalk, specifically to look at the cmDocsis20Capable MIB. The value for this MIB is 1, so that's obviously not it (most of the modems are SB5100 or SB5101, with some SBG901's).

We are still using DOCSIS 1.0 provisioning, so no service flows in the cable modem config files.

Any thoughts on why we might be seeing this behavior? Plant issues? Something else? Should we be upgrading the cable modem configs before doing any other troubleshooting?


Maybe it will help you.

Hi, maybe a older post from me will help you. In this post I will describe how to enable DOCSIS 2.0 Mode on Surfboard Modems.

This will also work for the SBG900-Series

MIB is okay, other commands to try?

Thanks for the response. I did see your previous post, and it is part of what led me to do the snmpwalk to check the MIB in the first place. Unfortunately, that MIB was already set correctly. Is it possible that the modem in question needed a hard reboot in order to re-register as DOCSIS 2.0? The behavior is very strange, considering that I believe that all of the modems were reset following the upgrade to atdma-tdma mode. FYI, the modem that I listed in my first post is a SBG901, so I would have expected that it would have registered as DOCSIS 2.0 as soon as its upstream modulation profile was changed.

Is there anything else I can look at, particularly regarding the other modems out there that are behaving this way? I'm fairly certain that the vast majority of modems on the system are DOCSIS 2.0 capable. Are there any command outputs that would be helpful to have?


There are actually two mibs

There are actually two mibs for Docsis 2, there is a standard Enable2.0mode and then there is the motorola enable 2.0... But you shouldn't need it for newer motorola modems like the sbg901, it really only applied to a few early versions of the old black surfboards. Motorolas can be a bit persnickety, a hard reboot sometimes is what it takes.


set in the snmp string of the modem file and make sure they have the current firmware


Some ideas off the top of my head

Well if I was in your shoes I might try some stuff like this on the troublesome modems :

* upgrade to latest CM firmware
* try the snmp set which tells the modem to forget its cached freqs etc.
* toggle that D2 mib off then on again
* try some different ways of kicking the modem, eg clear cable modem reset, clear cable modem delete, snmpset reset
* change the provisioning style to D1.1 (assuming you have no D1.0 modems left)
* if you get really desperate perhaps in the middle of the night temp flip the interface to from mixed to atdma straight mode to see if that trips the troublesome modems over to default to atdma. Drop it back to mixed mode after that.

in order for the sb51xx

in order for the sb51xx modems to use docsis 2.0 upstreams i.e. atdma or scdma they need the

Docsis2.0 enable set in their config file,
if they are running an older firmware they may also need the motorola specific mib set in the config file.

After the modem has come up with the Docsis 2.0 set in the config file it will not actually be able to use docsis 2.0 upstreams until you reboot it. The same applies when you set the mib, when docsis2.0 is set the modem announces itself as a 2.0 modem when it is registering otherwise it announces itself as 1.1. Newer modems don't have this issue because docsis20mode defaults to true in them.

There is also a weird error with Surfboard modems Sb510x models and cisco blades in tdma-atdma mode with certain modem firmware and ios (12.3 branch i think) combinations. If I remember right if you set the docsis2.0 enable in the config it fixes the issue, updating the modems firmware doesn't hurt either.

Log in or register to post comments