Netgear LM1200 SIM Card Setup

The Netgear LM1200 is a 4G LTE modem with an Ethernet port, often put in front of an existing router as a backup line. A ThingSIM works in it, but only after one setting that catches most people out: by default the modem does not connect when roaming.

Specifications and menu paths checked against Netgear's own documentation on 3 November 2026; sources are listed at the end. Menus can move between firmware versions, so if yours differs, follow the manual for your version.

What the LM1200 Is

An LTE Cat 4 modem with no Wi-Fi of its own. It hands a 4G connection to a router or computer over Ethernet. Netgear's UK product page now lists newer models, so the LM1200 may no longer be sold new in the UK.

Which ThingSIM Suits the LM1200

Compatible. The EU version (LM1200-100EUS) supports LTE bands 1, 3, 7, 8, 20 and 28 and 38, 40 and 41, covering the 4G bands used by all four UK networks. It takes one nano SIM (4FF): order a physical ThingSIM and push out the nano size. There is no eSIM.

As a backup line for a small office, UK 4-network 5 GB at £8.85 a month is the usual starting point.

Insert the SIM

1. Activate the SIM in the ThingSIM portal when you are ready to test; billing starts that day.
2. Make sure power to the modem is off.
3. Lay the modem flat with the bottom panel facing you and gently insert the nano SIM into the SIM slot on the rear panel.
4. Power the modem on. A red Signal LED means the SIM is not seated correctly.

Set Up Mobile Data on the LM1200

Connect a computer to the modem and open http://192.168.5.1; the admin password is on the modem's label.

1. Go to Settings → Mobile → Preferences. Change Auto Connect from the default “Always except when roaming” to Always, then click Submit. A ThingSIM connects to UK networks as a roaming SIM, so with the default setting the modem never connects on its own.
2. Go to Settings → Mobile → APN and click Add.
3. Give the profile a name. In the APN field, enter the APN shown in your ThingSIM portal when you activate the SIM, set Authentication to None and leave the username and password blank. Set PDP to IPv4.
4. Click Save, then select the radio button next to the new profile to make it active.
5. If the SIM has a PIN, manage it under Settings → Mobile → SIM Security.

Check It Is Working

The Dashboard shows signal bars, the network, the service type and the connection state; Settings → Mobile → Status Details has more. Then check that traffic reaches the internet through the router behind the modem, and look at usage in the ThingSIM portal.

Troubleshooting

• Never connects by itself: Auto Connect is still on “Always except when roaming”. Set it to Always.
• Connects to a network but gets no data: check the active APN profile. The profile also has a PDP Roaming field, which defaults to None; Netgear's manual does not say how to set it for a roaming SIM, so if data still fails, try setting it to IPv4 to match PDP.
• Signal but no data: check the SIM is activated in the ThingSIM portal, the APN matches the one shown in the portal exactly with no spaces, and data roaming is allowed. Then work through signal but no data in order.
• It worked, then stopped: look at the SIM's usage in the portal. A ThingSIM pauses when it reaches its monthly allowance; upgrade the plan straight away or wait for the reset.

Common Questions

Does a ThingSIM work in a Netgear LM1200?

Yes, in the EU version. Change Auto Connect to Always under Settings → Mobile → Preferences, add an APN profile with the APN shown in your ThingSIM portal and make it active.

Why does my LM1200 not connect automatically?

Its default Auto Connect setting does not connect when roaming, and a ThingSIM always connects as a roaming SIM. Set Auto Connect to Always.

What size SIM does the LM1200 take?

A nano SIM, pushed out of the ThingSIM trio card.

Related Guides

• 4G broadband backup
• Setting up a 4G router with a data SIM
• Netgear routers and modems
• APN settings: how to set up the APN on a device
• How much data does my device need?
• The best IoT and M2M SIM cards in the UK
• The UK 4-network 5 GB plan
• Compare every ThingSIM plan

Sources

Checked on 3 November 2026.

• Netgear LM1200 user manual (202-12163-03): www.downloads.netgear.com/files/GDC/LM1200/LM1200_UM_EN.pdf
• Netgear LM1200 EU/AU datasheet: www.downloads.netgear.com/files/GDC/LM1200/LM1200_EU_AU_DS.pdf