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# Understanding tracking numbers: groups, pools, and hierarchy

Tracking numbers in Nimbata can either live individually or under a group. The latter are collectively known as a 'Swap Group'. 

This article explains both and answers some related commonly-asked questions.

# The two levels

### Swap groups

A swap group is a named collection of tracking numbers that share the same source, call flow, and DNI swap configuration. 
The group name is what you see as the heading, e.g. "Austin - Google Ads" or "Phoenix - All Sources".

* The swap group is the unit that the DNI script works with. 
* When a visitor arrives from a matching source, the script pulls one number from that group's pool and displays it to the visitor. 
* All numbers in the group are interchangeable for this purpose.

### Tracking numbers

* The individual numbers listed under each swap group are the actual phone numbers in that pool. 
* Each one can be assigned a call individually or receive calls as part of the group's pool rotation.
* If you see two numbers under "Austin" and four under "Phoenix", that means Austin has a pool of two and Phoenix has a pool of four.
* The pool sizes were set based on the expected traffic volume for each location.

![](https://storage.crisp.chat/users/helpdesk/website/-/2/f/4/5/2f459a49cf382400/image_gyq7lh.png)

### Why multiple numbers under one group?

* A single number can only handle one simultaneous call. 
* If two visitors from the same source arrive at the same time, each needs their own unique number to maintain accurate session attribution.
* The pool exists to cover concurrent visitors. 
* The larger your peak simultaneous traffic, the more numbers you need in the pool.

Detailed Guide: [How to calculate the size of your tracking number pool](https://help.nimbata.com/en/article/how-to-calculate-the-size-of-your-tracking-number-pool-k4cca9/) 
Detailed Guide: [How many tracking numbers do you need?](https://help.nimbata.com/en/article/how-many-tracking-numbers-do-you-need-1paz293/)

### Do you need different numbers for different departments?

Not necessarily. 

The decision depends on whether you want to measure departments separately.
* If your goal is to route calls to different departments and you do not need separate reporting per department, a single call flow with a Keypad Entry (IVR) action can handle the routing. One pool of tracking numbers, one swap group, one call flow; callers press 1 for Sales and 2 for Support.
* If you want separate call volume reporting, separate conversion tracking, or separate workflow rules per department, then a dedicated swap group per department makes sense.

Detailed Guide: [How to add a keypad entry (IVR)](https://help.nimbata.com/en/article/how-to-add-a-keypad-entry-ivr-lld4g6/) 
Detailed Guide: [How to structure tracking numbers for multiple traffic sources](https://help.nimbata.com/en/article/how-to-add-new-tracking-numbers-1620sqg/)

### Can you use the same call flow across multiple swap groups?

Yes, you can. 

* A call flow can be assigned to multiple swap groups or individual numbers. 
* If your clients in Austin and Phoenix have identical routing logic, they can share one call flow. 
* Changes to that flow apply everywhere it is assigned.
* If one client needs different routing, create a separate call flow for them.

Detailed Guide: [How to set up call flows](https://help.nimbata.com/en/article/how-to-set-up-call-flows-1731pv5/)

### Can you duplicate a call flow to use for another client?

Yes. Rather than rebuilding a call flow from scratch for a new client, you can duplicate an existing project (which carries over the call flow structure) or manually recreate the flow using the same actions.

Detailed Guide: [How to create a new project, add multiple ones, or duplicate projects](https://help.nimbata.com/en/article/how-to-create-a-new-project-add-multiple-ones-or-duplicate-projects-yo2xa1/)
Detailed Guide: [How to set up swap groups](https://help.nimbata.com/en/article/how-to-set-up-swap-groups-1kng9t9/) 
Detailed Guide: [Tracking numbers 101: how to set up call tracking numbers with Nimbata](https://help.nimbata.com/en/article/tracking-numbers-101-how-to-set-up-call-tracking-numbers-with-nimbata-1ww2fxu/)