SIP 301 Moved Permanently

What SIP 301 means

The address has moved for good, and the response gives the new one. Unlike a 302, which is how call forwarding works day to day, a 301 says the change is permanent and your records should be updated.

Redirection (3xx)
Sent by A server redirecting permanently
Rare

What SIP 301 Moved Permanently actually means

The user can no longer be found at the address in the request, and the new permanent address is supplied in the Contact header. The distinction from a 302 is durability: a 302 expects to be temporary, a 301 is telling you to stop using the old address.

What causes SIP 301 on a business phone system

An extension or number has been permanently reassignedTypically after a renumbering exercise, where the platform redirects the old address rather than dropping it immediately.
A platform migration has moved the addressProviders use permanent redirects to move traffic during a migration.

How to fix SIP 301

Update whatever holds the old addressSpeed dials, BLF keys, directories and dial plans should point at the new address, since relying on a redirect indefinitely is fragile.
Confirm the redirect is expectedAn unexpected permanent redirect is worth querying with your provider rather than following.

Fixing the underlying problem

This page explains the code. These guides walk through the fix in detail.

Call forwarding and diverting

Questions about SIP 301

What is the difference between SIP 301 and SIP 302?

A 302 is temporary and is how everyday call forwarding works, so it is not something to fix. A 301 says the address has moved permanently, which means whatever is still dialling the old one should be updated.

Related SIP response codes

Source. SIP 301 Moved Permanently is defined in RFC 3261 section 21.3.2 and registered in the IANA SIP Parameters — Response Codes. The causes and fixes above are drawn from our own experience supporting UK business phone systems.

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