I have 2 routers at home:
- one connected to DSL (Deutsche Telekom)
- one connected to TV cable (Vodafone)
Therefore I actually have 2 VPN setups, both “L2TP/IPsec”.
Through time the VPN setups occasionally seem unfunctional. (Password change, …)
I asked Google AI Mode: How can I check with a networking tool, whether the L2TP/IPsec VPN server is accessible on my router?
macOS does not come with nmap. I already had macports installed. When I tried to install nmap, macports told me:
Current platform “darwin 25” does not match expected platform “darwin 24”
No big deal … – I had to upgrade – it told me how to do this. “_Free_wifi_Berlin” gave me incredible bandwidth, which allowed me to do this upgrade, while sitting in the university restaurant.
Is there a way to do a VPN connect to a L2TP/IPsec VPN server on the command line, and what command line options are there?
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“L2TP/IPsec” use 3 UDP ports. The router at the TV cable had one of them filtered. I was a little desperate – finally I gave up and turned to an alternative – see below!
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2026-10-01: I gave up using “L2TP/IPsec” to connect to both of them.
I turned to WireGuard instead – the set-up was easy, on the routers’ end and on my MacBook. (Thanks to Gerald D. for the hint!)
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