“18 Absent Subscriber —  Roaming restriction.” refers to a GSM / SS7 network error code (often seen in MAP signaling or SMS delivery reports).

Here’s a breakdown:

Meaning

Error Code 18: Absent Subscriber
This means the destination subscriber (the person you’re trying to reach) is currently not reachable in the mobile network. The home location register (HLR) or visitor location register (VLR) reports that the subscriber is absent — the network does not have a valid routing location for them.

Typical Causes

• The subscriber’s phone is switched off or out of coverage.

• The subscriber has roaming restrictions preventing them from registering on a foreign network.

• A temporary network issue (e.g., VLR or HLR synchronization problem).

• The subscriber’s SIM may be inactive or not allowed to roam by the home operator.

When It Appears

You’ll commonly see this code:

• In SMPP / SMSC delivery receipts (stat: UNDELIV, err:18, text: Absent Subscriber)

• In MAP signaling traces when trying to deliver an SMS or a call

• In SS7 error logs during location updates or message routing

Recommended Action

• Retry message delivery later — the subscriber may reconnect to the network.

• Verify that international roaming is enabled for that subscriber.

• If persistent, check with the destination network operator for roaming restrictions or provisioning issues.