Choosing extension numbers

Every user, auto attendant, call queue, and conference gets its own extension. Picking numbers from a consistent plan makes your system easier to manage: anyone can tell at a glance that 600 is a queue and 500 is a menu, and our support team can find their way around your setup faster.

Our recommended plan

Use 3-digit extensions for most businesses. Use 4-digit extensions if you have more than about 100 people or several locations.

Range	Use it for
100–199	People (each employee’s extension)
200–299	More people, once the 100s fill up
300–399	Shared lines: ring groups, a general voicemail box, a “front desk” line
400–499	Conference bridges
500–599	Auto attendants (phone menus)
600–699	Call queues
800–899	Anything else you need later

The plan is a convention, not a rule. The portal won’t stop you from putting a queue at 150. Following it just keeps things tidy as you grow.

Tip: If you have more than one building or office, use 4-digit extensions and let the first digit be the location: 1000s for the main office, 2000s for the second site, and so on. Callers and staff learn the pattern quickly.

Numbers to avoid

Some numbers are kept for the phone system itself or for public services. Don’t give them to a user, menu, queue, or conference.

• Anything starting with 0. Extensions can’t begin with zero.
• 2-digit extensions. They aren’t supported by default, and many dialing features won’t work with them.
• N11 numbers: 211, 311, 411, 511, 611, 711, 811, 911, and also 988 and 933. These are emergency, crisis, relay, test, or public information numbers. For example, 711 reaches relay services for callers who are deaf or hard of hearing, and 933 is the free 911 address test line.
• 700–799. These are kept for call park spots. Spots 700–729 work out of the box; 730–799 are held back in case you need more spots later. See Call park.
• 999. Used for account codes.
• 5000–5004. Used for checking voicemail and other system features.
• 7000–7999 (and 70000–79999 with 4-digit extensions). Used to send a call straight to someone’s voicemail.
• Numbers that start with 99 followed by an extension, such as 99101. Used for intercom.
• 8888. Kept for a special view-only account.

Letters after an extension

Behind the scenes, each person can have several phones, named with a letter after the extension, such as 101a or 101b. A few letters are kept for the ConnectUC apps and other integrations: m (mobile app), w (web and desktop app), t, and n. If you or your installer add phones by hand, skip those letters.

Heads up: Your extension can’t be changed after it’s created. Choose carefully when you add a user, because “changing” it later means creating a new user and moving everything over.

Want a local service number like 311?

If you’d like staff to dial a short code that reaches a local service, such as your city’s non-emergency line, contact Dial Raven support. We can set it up so the short code forwards to the right outside number, without using up one of your normal extensions.

Common questions

Can I mix 3-digit and 4-digit extensions?

You can, but it’s confusing for callers and staff. Pick one length for people’s extensions and stick with it.

What if I already used a number from the avoid list?

Some features may not work for that extension, or it may conflict with a system feature. Contact support and we’ll help you move it to a safe number.

Which numbers should my auto attendant tell callers to dial?

Your users’ extensions in the 100s (or 1000s). Callers never need to dial the extensions for your menus or queues directly, since the menu sends them there.

Related articles

• Add a new user or extension
• Build your first auto attendant
• Set up a call queue
• Set up a conference bridge
• Star codes: handy dial shortcuts