Call Routing by Caller ID

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It is sometimes called location-based routing, or A-number routing, or origin-based routing. The main idea is to determine the path of the call based on its Caller ID.

Routing by Caller ID is supported by both Kolmisoft softswitches: here’s a quick guide how to achieve this by using MOR and here’s an instruction how to configure this in M4 SBC.

Routing by Caller ID logic can be described in the following way: “If a call comes in from [Given Number], send that call to [Given Destination].” This will send all calls that follow the rule to the right department, individual, queue, voicemail, or anywhere else, or even block it.

Better user experience

Routing by Caller ID is used to connect different locations for better user experience.

Let’s take the example of a large company with offices in several cities. For better customer experience, the company has a countrywide toll-free number. The caller’s ID prefix feature has been configured to automatically transfer calls to the relevant office, based on the inbound Caller ID when that caller dials the company’s countrywide toll-free number.

To go even further, it is possible to route the call based not only on the caller’s ID prefix but on the entire Caller ID.

For example, suppose the same company has created a special office to handle VIP callers and to provide exclusive services. The VIP callers are identified by their Caller IDs and their calls are sent to the special office. They all receive a higher level of service in the handling of their calls.

Call blocking

There are cases when a system manager wants to block calls from certain prefixes; for example, in cases where Caller IDs match some pattern. Based on the prefix of the Caller ID, such calls are routed to some IVR or just dropped without notice. Various business applications can employ this tactic. One of them is the VoIP-GSM termination business.

SIM blocking

VoIP-GSM termination business is often said to be in the “grey area” or simply illegal in many countries. SIM cards with free calling minutes are employed to terminate traffic to the SIM’s operator network. At the same time, network operators use various methods to identify such offending SIMs and block them. Sometimes calls are sent from known Caller IDs to check the call route. If a SIM operator knows about these Caller IDs, they can be routed in a different way, bypassing the SIM cards and preventing them from being blocked.

Routing to avoid bigger charges (EU regulations)

On June 15, 2017, the EU introduced Regulation (EU) 2017/920, which eliminated all roaming charges for temporary roaming within the European Economic Area (EEA). Because of this, service providers now charge premium rates for calls not originating in the EEA.

In the past vendors would charge for calls based on the destination and on the location where a call was terminated. This made the rating very straightforward. In the last few years, however, to increase their profits, vendors have modified their operations to bill calls based on their origination in addition to the destination.

There are vendors who charge based on the Caller ID. So, in order to maximize profit, it is sometimes useful to route calls to the vendors who don’t follow this practice.


Routing by Caller ID enables identification of the caller to some degree, and to decide on call routing based on this. There are several use cases when it should be applied, and it is good to know about them in order to operate successfully in the VoIP business.

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