DSL Bonded Modems / Troubleshooting DSL

I put this article up for those like me that have what is called bonded DSL service with a provider like Sonic, and want to own their own modem.  For those that have a single DSL line with Sonic or others, finding a DSL modem is trivial (go to Amazon and get a TP-LINK TD-8817 for $25!).  For those that have two lines though (for double the upload/download speeds), the options are limited, and I will go over some of those options.  I also include some valuable general DSL troubleshooting information for all DSL installations.

In 2012 I got Sonic’s fusion service (2 phone lines, and bonded ADSL2+) using the ZyXEL P663HN-51 modem that I bought from Sonic as part of the install.  Unfortunately as many dslreports/Sonic/etc. forum users will report, these and other bonded ADSL modems can exhibit reliability problems (either from the get-go, or over time as they start to die).

So I thought — great all I do is call up Sonic and buy a new modem.  Well.  It isn’t so easy. (at least with ADSL2+ bonding, VDSL2 is easier to find)  Sonic is a great company, and I do recommend renting a modem from them if you aren’t a self-sufficient tech geek since they often go bad, need to be upgraded with better DSL tech, etc.  But I consider myself a tech geek, and $13/month for a rental ($156 a year) is a bit much considering fusion already costs about $120/month after taxes in San Francisco.  ($89.95 + insane taxes)

Therefore after much research, I determined a few good non-ZyXEL options / general solutions to try since Sonic stopped selling modems:

  • My favorite option (the one I use, and these models are VDSL2 bonded as well).
    * Buy a Pace (formally 2wire) 5168NV modem. (ebay, craigslist, etc)
    * Navigate to the http://X.X.X.X/upgrade URL (hidden URL) and load the following file:  (the ISP spiral does this for certain pace patches at )
  • Another option:
    * Buy a Comtrend 5631 modem. (ebay, craigslist, etc)
    * Perform a factory reset (hit the reset button with a paperclip edge for over 10 seconds).  When it asks for the ISP firmware, load the following file:
  • If you’re a geek and want to try unconventional options: (use VPI/VCI 0/35, bridged, automatic IP/MER)
    * buy a motorola/arris nvg289 modem — unknown if you can get this working as fairly locked down
    * buy a 6228-I2-200 modem (zphone/clear/paradyne/etc) — yes if you navigate to zphone and download the latest public CPE firmware you can get it working after tweaking with all the proper bonding settings — this GUI looks almost identical to the ZyXEL — so use MER and make sure failover and other bonded settings are checked — still an old modem so I wouldn’t particularly recommend
    * You may experiment with non-bonded modems like the aforementioned TP-LINK TD-8817, however based on my limited testing it seems like they don’t work with either line 1 or line 2.  (they sync up but you don’t ever get an IP assigned)
  • Unbond your setup.  Ask sonic/etc. for two discrete lines.  It is easy to find those single ADSL2+ modems on Amazon/etc.  Then either do your own bonding (won’t be quite as good as the ISP solution) using a wide variety of available network devices or manually split your traffic (customers vs in-house, etc.).
  • Wait for VDSL2.  (pretty soon)  If you’re around 4000 feet from the CO, it will mean you get bonded like speeds or more with a single line. (I’ll still keep two lines myself when this happens).  Potential options for bonded VDSL2 (not tested yet) include the Pace 5168NV already mentioned, the Zphone 6728-W1, the Actiontec V2000H/Q2000, the SGA432, etc.

On an unrelated note, to increase Sonic/other DSL providers reliability/performance within your building:

  • Replace your DSL modem (the point of this article).  I noticed immediately that the Pace 5168NV could negotiate higher up/down speeds vs the ZyXEL on both dSL lines.  The Pace modem also seemed to handle drops better by resetting itself/the connection vs the ZyXEL which would sometimes require a manual reboot.
  • Run new copper wire from the phone box to your modem directly.  (remember, 4 wires are necessary for bonded DSL since two lines are involved — lots of phone wire contains only 2 wires)  Heck if you can stick the modem right next to the phone box and run the CAT6 from the modem to the “network hub”.  Much better to have a long CAT6 to your electronics closet then to extend the copper DSL wire any further than you have to.
  • If you can’t run new copper wire, eliminate all excess copper wire in play.
  • Use high speed cables instead of standard phone cables when connecting your telecom equipment (modems, etc.).  (
  • Ask Sonic to dial down the max up/down speed so that your db levels increase beyond 6db.  (maybe until you see 7db SNR).  This many only hurt performance slightly, but can increase reliability dramatically.
  • Verify you have DSL filters for all phones/faxes/etc.  Replace them since they are cheap to verify you don’t have bad ones or low quality filters.
  • Ask a Sonic tech to come out and evaluate the situation, including asking AT&T for a vendor meet to diagnose any issues on their side.  Also ask if there are any excess bridge taps in place.  (  This can be responsible for a ridiculous amount of extra cabling between you and the central office compared to the linear distance.
  • Consider Annex M mode instead of the default Annex A mode to get less download and more upload speeds.  You might be surprised at the upload speed being your bottleneck vs the download speed.   ( -> Labs -> Fusion Line Profile -> Upload profile [Download returns back to Annex A profile])
  • Consider Interleave sync configuration to get more latency but more reliability in return.  ( -> Labs -> Fusion Line Profile -> Interleave profile [Fastpath returns back to low latency])
  • Work with your ISP!  Just be patient.  Sonic techs are great in particular.  I wish one day these ISPs would have a NOC to evaluate all the drops and followup proactively, but I think that is unattainable at the moment.  (if they did this, they would have the knowhow to instantly solve almost any problem due to their breadth of experience in troubleshooting all possible issues)  As it stands the ISPs often struggle a bit to nail down what is happening and lean on the customer to be persistent but the good ones try hard at least. (you still have to be your own advocate in my experience)
  • Reduce your network switches beyond the modem/router to as few as possible and choose as high quality as possible.
  • Use non-wifi/CAT6 cables when you can to all your devices that need to be on the network.
  • Use a high quality wifi router after the DSL modem (ASUS RT-AC87R).  Don’t blame anyone but yourself if the service is great when connected to the DSL modem but stinks otherwise.  Don’t depend on the DSL modem’s wifi being great.

On one more unrelated note, you may ask why the heck I’m using DSL in San Francisco for $120/month.

  • Astound is not on my block even though it is in my zipcode.  No-go there, no interest from them.
  • DSL is often more reliable than cable with regards to random drops since it is often less shared.  Astound/Comcast have given me great speeds at other bay area locations but reliability and latency have often been a joke.  Also modern bonded DSL speeds (and regular VDSL speeds) aren’t bad by any means (I’m ok with >15mbps, with the upcoming VDSL it should be more like 40mbps)
  • Comcast is on my block, but likes charging buildings not yet hooked up to them $41,000.00 (no joke) on my block to expand their infrastructure since many businesses in SF can afford this.  Yes.  It costs $41,000 to run a Comcast cable a few hundred feet underground.  San Francisco politicians should probably get involved here…
  • Monkeybrains is great.  But I have no line of sight to them.  (oh well)  Maybe they’ll come up with a great design for a really tall antenna for customers like me.
  • I could use another DSL provider.  (DSL Extreme comes to mind since you can buy a modem directly from them and not rent it, or Raw Bandwidth, Fastmetrics) But wow Sonic’s technicians are amazing and I like reading Dane Jasper’s posts (the CEO of Sonic) – I hope they succeed where others have failed to bring fiber/etc. here in San Francisco.
  • Yes does work.  (you can still buy their devices on ebay) I use that as a backup.  But even though Clear/Sprint is unlimited wireless, it is still 4G/higher latency/6mbps max.
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