Month 8: VPN, ping and cell towers

Where VPN settings live

Apple devices have built-in L2TP, IKEv2 and IPSec VPNs; other protocols need a third-party app. On iPhone and iPad: Settings > General > VPN & Device Management (or tap a VPN profile from IT). On a Mac: System Settings > Network > Action menu > Add VPN Configuration; existing ones are in System Settings > VPN with the Info button.

Exam tip Get the type, server address, account and authentication method from the network administrator first.

Reading the settings

Each service shows a status, Connect/Disconnect and an Info button.

• Remote ID and Local ID: IKEv2 only
• Connect on demand: starts the VPN automatically when needed
• L2TP options: disconnect on user switch or logout, send all traffic over VPN, verbose logging
• VPN connects but internal names fail: check the VPN's DNS servers and search domains (nslookup)

Scope first, then one change at a time

Find out whether the problem is the device, the network or the remote device. Start simple: is the device online, does it work without the VPN, is the right VPN type chosen, are the credentials, shared secret or certificate right? Test from another network (cellular or other Wi-Fi) to isolate network-specific problems, and change one thing at a time.

• Mac: try a new network location to test clean settings
• Check for MDM profiles that enforce network settings
• Mac tools: ping, traceroute, ifconfig, networksetup, scutil; Console for VPN logs
• Still failing with good settings and credentials? Escalate to the network administrator

Is anyone there?

ping (in Terminal) checks whether the Mac can communicate with another device. Type ping and an IP address, press Return, then Control-C after a few replies. Each reply shows bytes, the ICMP sequence number, the ttl and the round-trip time. The statistics should show packets transmitted = received and 0.0% packet loss.

Exam tip Some devices and servers block ping. No reply doesn't always mean the device is down.

Narrowing it down

If the target doesn't answer, ping devices in other locations: the router, another computer. If they answer, the problem is the remote device or its connection. If nothing answers, keep troubleshooting this Mac's connection.

$ ping 10.0.0.25
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
^C
--- 10.0.0.25 ping statistics ---
3 packets transmitted, 0 packets received,
100.0% packet loss

Data for the specialist

A Wireless Diagnostics report collects detailed data about the Mac's Wi-Fi environment while the problem is happening, for a network specialist to analyze. Quit apps, join the problem network, Option-click the Wi-Fi status icon and create the report. Add details (like 'drops in the back conference room') and the access point name in the summary.

• Saved in /private/var/tmp as WirelessDiagnostics_....tar.gz (many files, compressed)
• Monitoring for drops runs while the Monitor pane stays open on the same network

No Service, Searching, SOS

No Service, Searching, SOS only or SOS in the status bar mean the device can't connect to a cellular network. First confirm there's coverage. Then turn Cellular Data off and on (Settings > Cellular) or toggle Airplane Mode. Abroad, turn on Data Roaming in Settings > Cellular > Cellular Data Options, if the plan allows it.

Exam tip A device management service can restrict cellular settings. Check with the MDM admin.

Carrier settings updates

Carriers send carrier settings updates that improve connectivity and can add features like 5G or Wi-Fi Calling. Users get a prompt; a mandatory one shows OK instead of Update. To check by hand: Settings > General > About (the version is next to Carrier).

eSIM

An eSIM activates a plan without a physical card; iPhone 14 and later bought in the US are eSIM only. Manage plans in Settings > Cellular (label, remove with Remove Cellular Plan). A deleted eSIM must be re-issued: get the details from the carrier or network admin, then Settings > Cellular > Add eSIM. Activation fails? Keep Wi-Fi on during setup, update iOS, and confirm the carrier has the profile ready.

Physical SIM and SIM PIN

Invalid SIM or no SIM: remove the tray, inspect the card, reseat or replace it, then check service. Locked SIM means a SIM PIN is set. Never guess the PIN: wrong tries can lock the SIM for good. The carrier has the default PIN and the PUK code; 'PUK exhausted' means a new SIM or eSIM.

Mr. Barkley: So I should NOT try 1234 five times?

You: Please do not.

What changes in the 27 releases

On iOS 27 and iPadOS 27, the setting called Wi-Fi Assist (which uses cellular data when Wi-Fi is poor) is renamed Connectivity Assist. The device management key behind it doesn't change. Expect the new name in 27-era questions and in Settings.

Exam tip Coming in iOS 27: not on the iOS 26 exam (last exams Oct 30, 2026). Apple's iOS 27 course opens Oct 29, 2026.

Where and what

Built in: L2TP, IKEv2, IPSec (others need an app). iPhone and iPad: Settings > General > VPN & Device Management. Mac: System Settings > Network > Action menu > Add VPN Configuration; later changes in System Settings > VPN.

• Remote ID and Local ID: IKEv2
• Connect on demand: starts the VPN automatically when needed
• Connects but internal names fail: the VPN's DNS servers and search domains (test with nslookup)
• Basic checks: online without VPN, right VPN type, credentials and shared secret or certificate, another network

Can this Mac reach that device?

ping tests whether the Mac can communicate with another device. Type ping and an IP address in Terminal, wait for a few replies, then press Control-C for the statistics: packets transmitted should equal packets received (0.0% packet loss). Each reply shows bytes, sequence number, ttl and round-trip time.

Exam tip One device silent but others answer: suspect that device. Nothing answers: troubleshoot this Mac. Some servers block ping.

No Service, Searching, SOS

These status messages mean no cellular connection. Confirm coverage, then turn Cellular Data off and on (Settings > Cellular) or toggle Airplane Mode. Abroad: Data Roaming in Cellular Data Options, if the plan allows. Carrier settings updates (check in Settings > General > About) improve connectivity and can add 5G or Wi-Fi Calling; a mandatory one shows only OK.

eSIM, SIM and SIM PIN

Manage eSIMs in Settings > Cellular (label, Remove Cellular Plan, Add eSIM). A deleted eSIM must be re-issued by the carrier or network admin. US iPhone 14 and later are eSIM only.

• Invalid SIM: remove the tray, inspect, reseat or replace the card
• Locked SIM: never guess the PIN; the carrier has the default PIN and PUK
• eSIM activation fails: Wi-Fi during setup, update iOS, confirm the carrier's profile, restart