What is routing by caller number?

What it actually is

Every incoming call arrives with a caller ID — the number it was dialed from. In most phone systems, that number is only shown on the phone's screen. With caller-based routing (Caller ID routing, sometimes called CLI routing), the PBX uses it to make a decision: before it plays a menu or sends the call to a queue, it checks whether the number appears on a list you set up, and if it does, it sends the call to the destination you chose for it.

The idea is simple: not every caller needs the same route. A longtime customer who calls every week shouldn't have to hear "For sales, press 1" every time. A manager calling from his cell phone wants to reach the secretary directly. And a number that harasses the office ten times a day shouldn't reach anyone.

Caller-based routing is one of the layers of the call flow, and it is checked early — before the menu and before the queue. That's why a caller rule can override everything that comes after it.

How it works

1. The call comes in to the organization's number, along with the caller's number.
2. The PBX compares the number against the list of caller rules defined for this number.
3. If there is a match — the call goes straight to the rule's destination: an extension, a queue, another menu, a message, or a hang-up.
4. If there is no match — the call continues as usual: the hours check, then the menu or the regular destination.

Two important things to understand. First: the comparison is against the full number, exactly as it arrives. If a customer sometimes calls from the office and sometimes from a cell phone, you need to enter both numbers. Second: the rule depends on what the network passes along. A caller who blocks their caller ID ("private number") won't be identified, so a VIP rule won't work for them — they will go through the regular route.

A caller rule can also be combined with time. For example: the big customer goes straight to their account manager, but outside business hours to the on-duty person's cell phone. That way the rule doesn't send a call to an empty extension when no one is there.

Common uses

• VIP customers — numbers of key customers skip the menu and go straight to the account manager or to a priority queue.
• Suppliers and regular contacts — the accountant, the delivery company, the regular vendor — straight to the person who handles them.
• Management — the director calls from his cell phone and reaches the secretary's office directly, with no menu.
• Yeshiva parents — parents' numbers can go to the menu that fits them, without passing through the options for vendors and the office.
• Language — callers from abroad, by their country code, reach a menu in English or an agent who speaks the language, if the system can identify the prefix.
• Blocking — harassing numbers don't get through at all, or they hear a message and are disconnected.

What all these uses have in common: the rule saves the caller a step that isn't relevant to them, or saves the organization a call it doesn't want. It's best to start with a short list — ten or twenty numbers that really matter — and expand only once you see it works. A list of hundreds of numbers is hard to maintain, and quickly fills up with numbers that are no longer relevant.

Real-life examples

A building-supplies business. Ten regular contractors bring in half the revenue. Their numbers are set up as caller rules, and when they call they go straight to a small queue of two veteran salespeople. Everyone else hears the regular menu. The contractors feel recognized, and the general queue frees up.

A service center. A customer who calls twenty times a day and overloads the center gets a rule that sends them to one agent who knows the case, instead of landing on a different agent every time. This saves time for both the customer and the staff.

A nonprofit. Major donors who call reach the coordinator who handles them, and not the general donations line, which is very busy on the evening of a campaign.

Which rule wins

Where caller-based routing gets complicated is when it collides with other rules. What happens when a VIP customer calls outside business hours? What happens when their number appears in two rules? What happens when the call arrives through a different number of the organization?

The general principle: the PBX goes through the rules in order, and the first one that matches decides. A caller rule is checked before the hours rule, so it can "override" the closing message — unless you defined for that rule itself what to do outside business hours. This is exactly the situation where an important customer calls at night and reaches the extension of an account manager who is already home.

The safe way is not to guess, but to see. A diagram of the route, showing all the rules in order and which one takes priority, saves a lot of "why did that happen?"

Common mistakes and tips

• Only one number per customer — the customer calls from their cell phone, reaches the regular menu, and is surprised. Enter all of their known numbers.
• A forgotten rule — a customer who left, an employee who was replaced, a vendor you no longer work with. Go over the list once a quarter.
• A destination with no backup — the rule sends the call to one person's extension. When they don't answer, where does the call go next? A small queue or a hunt group, with a voicemail box at the end, is better.
• Blocking too broadly — blocking by an entire prefix can block customers too. Block specific numbers.
• Relying on a private number — you can't route by a number that doesn't arrive. If it matters, ask the person to call with their caller ID showing.

The VIP list: how to manage it so it doesn't fall apart

A good VIP list is short, documented and maintained. Here is how the building-supplies business from the example above manages it:

1. Who gets in. Set a clear criterion: the ten biggest customers by annual turnover, not "whoever complained last week." Without a criterion, the list grows until everyone is a VIP and no one is.
2. Which numbers. For each customer, write down all the numbers they call from: office, the owner's cell phone, the purchasing manager's cell phone. Three or four numbers per customer is normal.
3. Where to. The destination is a small queue or a hunt group, not one person's extension. If the contact is on vacation, someone else answers.
4. One spreadsheet. The customer's name, the numbers, the destination, and who approved. The spreadsheet is the source; the control panel reflects it.
5. A quarterly review. Once a quarter, go over the spreadsheet: who is no longer a customer, who changed numbers, who needs to be added.

How many numbers is reasonable to keep? In a small business, 10–30 numbers. With a list of hundreds of numbers, no one knows anymore why each one is there, and then a customer who left two years ago still goes straight to the manager.

Blocking harassing numbers — without hurting customers

A harassing number is one that calls again and again for no reason: telemarketing, a caller who hangs up, someone who has already been told no. Blocking is a caller-based routing rule whose destination is a hang-up or a message. There are three ways to block, from gentlest to harshest:

• A message, then a hang-up. "This number cannot connect to the office." The caller understands it's deliberate and stops trying. Suitable for most cases.
• A silent hang-up. The call drops with no message. Suitable for auto-dialers, which aren't listening anyway.
• To a dedicated voicemail box. The caller can leave a message, and someone looks at it once a week. Suitable when you're not sure, for example a number that calls at night and hangs up.

Three rules of caution: don't block by an entire prefix (see below); write next to each block when and why; and after a week, check the call log to see how many calls were blocked. If the blocked number suddenly shows up with a call duration, the rule isn't taking effect, and perhaps the number arrives in a different format (with or without the country code).

Routing by prefix — what it is, and when it's risky

In many phone systems you can define a rule not only for a full number but for the beginning of a number: everything that starts with 1 (the US country code) goes to an English menu, everything that starts with 44 goes to an agent in London, everything that starts with 05 goes to the cell-phone queue. This is useful for an organization that serves communities in different countries and wants a language based on where the call comes from.

The danger is in blocking by prefix: "everything that starts with 072 is harassing" also blocks a customer whose business number starts that way. Routing by country code isn't always accurate either — an Israeli customer traveling abroad who calls from there will reach the English menu. So: a prefix for language routing — yes, with care; a prefix for blocking — almost never.

In any case, a rule for a full number overrides a rule for a prefix in most systems — the more exact match wins. It's worth verifying this on the call flow screen rather than assuming.

A full example: a VIP customer calls — twice

A moving company with ten large customers. One of them, a chain of stores, calls from four numbers: the orders office, two cell phones of branch managers, and the management line. All four are on the list, and the destination is a hunt group called "Large Customers" — two veteran reps in the first tier, the operations manager in the second, and a voicemail box that is sent to all three.

First call, Monday 11:00. A branch manager calls from his cell phone. The PBX recognizes the number even before checking the hours, skips the menu, and rings both reps. One answers within 8 seconds and sees "Large Customers" and the number on the screen. The customer never heard "For sales, press 1."

Second call, Monday 22:30. The same manager, a truck is stuck. The rule matches now too — but the "Large Customers" group is protected by a time group: outside business hours it skips the reps and rings the night-duty person's SIM extension directly. Without this protection, the call would have rung in an empty office — exactly the collision described above.

What makes this possible is the decision to point the rule at a group and not at a person: a group has tiers, hours and a final destination; a single extension doesn't.