Establishing a Dial Plan

One of the most overlooked and often under planned things with telephony installations is/are the dial plans. There’s a lot of things you need to think about when taking in to consideration a dial plan…

  • Extensions
  • Outgoing line(s)
  • Paging Zone(s)
  • Room for expansion
  • Trunking

…and many more things. As an example, I’ll take my configuration at my house. From a high level, I have about 15 phones. Initially most people would look at the SMB scenario I have at my house and think let’s create 3 digit extensions – heck, some might even go with two digits to keep it simple. If we take two digits, once I have my initial 15 extensions set up and an outgoing line as well as parking an paging, I’m almost 1/3 of the way done with my extensions and I haven’t even grown, nor have I trunked to any other systems.

Next, there’s the option to go with a three digit dial plan…offers much more flexibility and room for movement, but if I plan on having remote locations or even trunking to another system, three digit plans can be consumed quick or even overlap. Next is 4 digits. Probably a good, “safe” bet for most, but I opted for 5 digits and here’s why (and how I set mine up)…

With 5 digits, I can easily integrate in to just about any other system and if I need to change my 15 extensions, it’s not much of a burden, not to mention that my dial plan really “fits” well with 5 digits. I chose to start all of my extensions with 7. Now, here’s one thing to note – just because my dial pattern is “defined” as 5 digits, doesn’t mean I can’t use 3 digit monikers in the plan…Watch how this works:

My 15 extensions are 5 on my desk (for testing, work, etc), 2 in the bathrooms, 3 in the downstairs living area, 3 in the bedrooms and 2 in remote locations. I logically grouped them this way for various reasons. First lets start with the three in the living area – they all start with 72xxx:

72027 – Living Room
72127 – Living Room 2
73127 – Kitchen

With those three extensions, I now also have a ring group 72000, which rings all of the phones simultaneously and a page group, 72999 which pages all 3 phones. Noting that strategy, lets look at the desk phones:

77027 – Nortel 1120e
77127 – Nortel 1140e
77227 – Nortel 1210
77327 – Nortel 1230
77427 – Nortel i2004

Guess what…I’ve also got 77000 which rings all 5 and 77999 which is a page zone for all 5. The bedroom phones follow a 73xxx pattern with 73000 and 73999 doing the same. Bathrooms, 74xxx with 74999 and 74000 as their page and ring group/zones. Lastly the other two odd ball (remote) phones, I have as 76xxx and 78xxx. They didn’t need page zones or ring groups as they stood alone as their only extensions.

Now, what’s interesting is you’ll note I didn’t use 70xxx nor did I use 71xxx or 79xxx. That’s because I created three special dial patterns with those digits:

700 rings all phones
799 pages all phones
71 followed by digits was left as an outgoing trunk pattern (if needed)

So, as you can see, I’ve left quite a bit of flexibility in the dial plan while also allowing for trunking (I’m trunked to a 4xxxx dial plan to Joe in Chicago) and the ability to add further extensions in the future – or growth of quite a few extensions 🙂 Main point being, think about your dial plan before just taking the easy route because what might be easy now can become difficult later and a lot of up front planning can make for a smooth ride downstream 🙂