Increase Default Conference ID Length

Upon initial install of a new Skype for Business pool, the dial-in conference ID will be 5 digits long. The conference ID is the part you enter via your phone number pad so that dial-in conferencing can route you to the correct meeting. Over time, as your organization grows, the length of this conference ID can grow to be rather large. I've seen it as long as 12 digits.

As conference ID's get too large, the guidance is to create new conference directories.

So there is a method to help keep conference ID's short.

But what of the opposite approach? For whatever reason - usually security is involved here - you must have at least 7 digits in the conference ID. So starting with the default 5 digits and organically growing it to 7 digits is a non-starter.

Interestingly, the fix for a larger conference ID is the same as shortening the conference ID: Create more conference directories!

If you scanned the article I linked to, you'll have seen this overview of the conference ID:

<housekeeping digit (1 digit)><conference directory (usually 1-2 digits)><conference number (variable number of digits><check digit (1 digit)>

What I am interested in here is the second section - the conference directory. It turns out that the ID you create using the New-CsConferenceDirectory cmdlet has a direct correlation to the length of the conference ID.

If you are building your very first pool, the installation process will create a conference directory for you. And the Identity of that conference directory will be "1". I can search my lab environment to see which pool was created first by using this cmdlet:

Get-CsConferenceDirectory | ?{$_.Identity -eq "1"}

Below is the output of that cmdlet.


That is also the only conference directory on that pool. So all users on that pool will start off with 5 digit conference ID's. As more and more meetings are created, eventually this will expand to 6 digits (and more).

On a different pool, I have to have conference ID's that are at least 7 digits long. How do I accomplish this? I do this by creating new conference directories and setting the value of the Conference ID to a number between 1,000 and 9,999.

Here's a little script to create 10 new conference directories whose Identity is between 1,000 and 1,009





New-CsConferenceDirectory -HomePool -identity $i


until ($i -eq 1009)

After running this I can see that I now have 10 new conference directories whose identity value starts at 1,000 and ends at 1,009.

Get-CsConferenceDirectory | ?{$_.Identity -gt "1000"}

Below is a snippet of the output.


Now I log in as a users on that pool and create a new meeting. Note that the conference ID is seven digits long.


In summation, you can both increase and decrease the length of a conference ID by judicious use of the New-CsConferenceDirectory cmdlet. Also note that you can create 6 digit conference ID's by using conference directory identities between the range of 100-999 inclusive.

Note that you will have to run Remove-CsConferenceDirectory  or Move-CsConferenceDirectory to remove any of your conference directories that have an Identity lower than 1,000. Any conference directory on a pool can be used and if you still have your original conference directories with single, double. or triple digits in size, then conferences with less than 7 digits will still occasionally be created.

Comments (4)

  1. soder says:

    Welcome back, Flinch! I hope you will be frequent author on nexthop!

  2. Akampa says:

    Very Useful info , remember having similar discussion in the forums

  3. Jon BIrkett says:


    Useful post. I assume this was tested using dynamic rather than static dial-in conference IDs? Do static dial-in conference ID’s follow the same logic?


Skip to main content