Mind the Gap... Between VoIP and Analog

Around five years ago my company made the decision that at some point in the future we would be replacing our phone system with a VoIP system.  As part of that decision we decided that it was no longer smart to run separate voice and data wiring on new projects.  This led us to a problem of how to make the connection between data patch panels and the existing voice 66 blocks.

Unfortunately we didn't go straight to the solution we are using now.  Our first solution was to take voice cross connect wire and terminate it with an 8p8c connector on one end and then punch down the other end to the 66 block.  For one or two links, this solution worked ok, but scaling the solution ended up with a rat's nest of cross connect cables.  

The next solution was basically the same as the first only we using CAT6 patch cables with one 8p8c cut off.  It was easier to keep the cabling neater, but it still didn't scale well as the thicker cables got in the way on the 66 blocks.

Finally we came to the solution that I want to share.  We started buying Panduit 24 port 1 pair voice panels.  These panels have a RJ-21 connector on the back that splits a 25 pair cable into 24 RJ45 jacks with 1 pair connected to pins 4 and 5 of each jack.  When combined with a 25-pair amphenol cable and a prewired 66 block, it makes a very modular and convenient way to bridge the gap between data and analog voice cabling. In this configuration I often put the voice panel with my switches as it serves as a "voice switch" in the rack. 

During the last five years this has served well and I believe that it will also help support our large analog deployment that will remain with our new VoIP system.  Hopefully our trial and error will help someone else out.

Hey Window! You Make a Better Door Than You Do a Window.

Over the past two months, I have been battling with a Cisco Aironet 1310 wireless bridge between our main building and a physician's office that we rent across the street.  This physician's office is one building out of a cluster of 15 in a "Doctor's Park".

A few years ago when we put in this link, we were the only wireless in the area.  Within the last 6 months several of the physician's offices and a neighboring nursing home have added wireless infrastructure.

When our problems started, I noticed that our signal strength had gone from an average of -69dBm to -82dBm and our signal to noise ratio was around 10 dBm.  My first thought was obstruction having recently had a different link knocked out by a new HVAC project on the roof of one of buildings interfering too much with the Fresnel zone of another link.  I went up to where the radio was on the main building and took a look.  Nothing new was in the line of site.

Having ruled out the obvious, I fired up the Cisco Spectrum Expert on my laptop and sat up near the radio.  Almost immediately I saw something that wasn't quite right.  All of my APs and bridges are set to use channels 1, 6, or 11.  On the laptop though I was seeing active APs on channels 3 and 8.  Of course since the 2.4Ghz channels overlap, this was causing cross channel interference on all three of the channels that my bridge was configured to be able to use.  As I looked more closely at the Cisco Spectrum Expert information I found the SSIDs associated with these interfering APs.  This is where I got a break, I recognized one of the SSIDs as being from another healthcare entity from another town.  I went back to looking outside and thinking where this might be coming from.  Eureka, one of the physician's offices had a new sign out front with the other entity's logo.  Thankfully the network engineers on their side were gracious enough to reconfigure their stand alone APs to use channels 1 and 11 leaving me 6 for my bridge.

You're probably asking, what does this have to do with a window being a door?  Well yesterday after having resolved our bridge issues for almost a month by my detective work, the problem came back.  This time though, I couldn't find any interference.   Instead, the screen showed something on channel 6 with a very high duty cycle.  I confirmed it was my bridge that was on channel 6.  This puzzled me so I drove over to the far end of the bridge to see if something was amiss there.  I walked up to the radio with my laptop and saw the same type of high duty cycle, but again no interference.

As I did a visual sweep of the room I saw that the window in front of the AP (I know this isn't ideal, but we rent the building.) was partially open such that the metal frame of the window was just about centered in front of the radio.  I asked the clinician whose office it was how long the window had been open.  They told me it had been open for about 2 hours... exactly the amount of time that the bridge had been having problems.  I promptly closed the window and presto the signal strength went back to normal and the duty cycle returned to normal as well.  Once again, the network was undone by the Human Network.