PLMN

A PLMN (Public Land Mobile Network) is a mobile network run by a licensed operator for public use, identified worldwide by a PLMN ID made of its mobile country code and mobile network code (MCC/MNC). When a modem reports an operator code such as 310260, it is naming a PLMN.

PLMN types

Term	Meaning
HPLMN	Home PLMN — the network whose MCC/MNC matches the subscriber’s IMSI
EHPLMN	Equivalent home PLMN — another PLMN ID the home operator treats as home
VPLMN	Visited PLMN — a network the device uses while roaming
RPLMN	Registered PLMN — the network the device last registered on
Forbidden PLMN	A network the device must not try again automatically, stored after certain rejects

How PLMN selection works

3GPP TS 23.122 defines how a device chooses a network. In automatic mode it generally tries the last registered PLMN first, then the home PLMN (or equivalent home PLMNs), then networks in the user-controlled list, then networks in the operator-controlled list stored on the SIM, and finally any other PLMN with adequate signal. Each list entry can be paired with a preferred radio access technology (RAT).

The operator-controlled list is a key lever for steering of roaming: the home operator updates it to point roamers at preferred partners. When a network rejects registration with a cause such as #11 “PLMN not allowed”, the device adds it to the forbidden list and moves on (see attach reject cause).

Where PLMN IDs show up

• In the system information every cell broadcasts.
• In modem responses such as AT+COPS?, which report the current operator and access technology.
• In roaming agreements, steering lists and partner databases.
• In test plans, where each home network × visited network pair is a separate case.

Why it matters for testing

Forcing a specific PLMN is one of the most useful controls in roaming and coverage testing: it shows whether a profile can register on each partner network rather than only on whichever network the device happens to pick. SimCheck.ai tests can force the operator by PLMN, and PLMN Hunt runs on your own edge devices scan for target networks and attach when one appears — see PLMN hunt and network monitoring.