Dial plans are a fundamental component of setting up Cisco Communication Manager. They’re such a crucial part, in fact, that 11 percent of Cisco’s CCNP Collaboration exam material covers dial plans — and CBT Nuggets trainer Chuck Keith recently produced an entire course explaining them.
Here are a few of the best practices for dial plans, and some ideas worth thinking about when you are tasked with implementing or designing a VOIP system of your own. What follows are some basic outlines of Dial Plan best practices, and while not overly detailed, they definitely are worth thinking about if you are working in a Cisco environment.
1. Understand route patterns
In order to properly implement Cisco’s best practices into your dial plans, you need to understand route patterns. Route patterns are an integral part of a Cisco CUCM setup and need to be configured properly if you are going to dial outside of your organization and connect to different services.
In order to make calls to your PSTN or through a SIP gateway, your route patterns will have to be configured so that the system can determine how a call is routed, and where the call will go. To do this, a dial pattern needs to be matched.
2. Don’t forget dial plan hierarchy
Dial plan hierarchy can be thought of as a service that uses a best match type of logic. For instance, if a device has access that matches a pattern based on CSS and a partition is assigned that matches patterns within the CUCM, then the CUCM will look at all of the DNs and pattern that match with the highest probability.
An example would be a TP of 33XX and an RP of 2XXX, in the case of the former, it has more detail and would more easily be matched, while the latter would not. It is important that the initial dial plan hierarchy is thought out well ahead of time so that you can implement best practice to your setup.
3. Grouping Endpoints
Your organization likely uses a variety of endpoint devices (IP phones, analog phones, even fax machines and applications (voicemail, conferencing systems, etc.). If so, consider organizing these endpoints into special groups.
Doing this allows these groups to handle incoming calls for services based on different rules: top-down, circular, longest idle, and broadcast. Calls are dictated to endpoints by the digit analysis function, which is where call privileges are implemented.
Endpoint addressing and call coverage are two crucial functions of Cisco dial plans, so it’s important to consider whether you want to group endpoints when designing and implementing your dial plans.
4. Configure redundant paths/failover in your system
If one of your main systems goes down, it is important for you to have a redundancy plan. This might come in the form of having multiple database failover and replication or having a secondary live system that kicks in as a backup if the main PUB goes down. Your PUB holds all of the DB in different clusters and it sometimes also houses the CUCM.
5. Understand your digit manipulation needs
Digit manipulation is typically used for caller ID purposes for outgoing PSTN calls.There are many different factors to take into consideration, depending on your current setup and its location.
You might have a need for digit stripping for specific number formats or you might need to have numbers added to a dialed number. All options are available for configuration within the CUCM and there is a lot that needs to be considered when you want to apply a best practice element to your dial plan.
Having room to grow is always recommended as part of any IT best practice outline, and your telephony systems are no different. This means that if your organization ever gets bigger, you will have the necessary resources to allocate to additional members. The same is true of an organization that is looking to downsize; having the relevant plans in place to assist with movement in either direction.
There are a lot of different avenues to consider when looking to use a modern VOIP system as provided by Cisco and their CUCM service. This is by no means a definitive guide to best practice, but it should serve as inspiration when you decide to take a look at implementing such a solution or looking at studying for your CCNP. Check out Chuck’s material on the subject and take a look at some of his YouTube videos relating to all things networking and Cisco.