L2TP VPN not working KDE Connections Fedora

Hardware Hub Networking
1

Hey guys,

Banging my head against the wall with trying to get a L2TP tunnel going between my laptop and a UniFi USG at a remote site. AFAIK all the settings in the connections manager are correct but it fails to create the tunnel. Every time I try I just get a popup alert saying it failed. Any advice?

Jun 07 17:06:36 kelpie NetworkManager[1380]: <info>  [1654643196.6955] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: Started the VPN service, PID 113718
Jun 07 17:06:36 kelpie NetworkManager[1380]: <info>  [1654643196.7008] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: Saw the service appear; activating connection
Jun 07 17:06:36 kelpie NetworkManager[1380]: <info>  [1654643196.7191] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: VPN connection: (ConnectInteractive) reply received
Jun 07 17:06:47 kelpie NetworkManager[1380]: <info>  [1654643207.0404] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: VPN plugin: state changed: stopped (6)
Jun 07 17:06:47 kelpie NetworkManager[1380]: <info>  [1654643207.0410] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: VPN service disappeared
Jun 07 17:06:47 kelpie NetworkManager[1380]: <warn>  [1654643207.0411] vpn-connection[0x5613f80c2150,97703148-5cb5-439c-a5fd-86f16ad048dc,"Upper Mine",0]: VPN connection: failed to connect: 'Remote peer disconnected'```
2

If you are using NetworkManager-l2tp with libreswan (which no longer supports the weak modp1024 algorithm), you could try switching to strongswan with :

sudo dnf install strongswan
sudo rpm -e libreswan

Unrelated to this issue, but as you are using Fedora, I would suggest removing the blacklisting of L2TP kernel modules with the following commands:

sudo sed -e '/blacklist l2tp_netlink/s/^b/#b/g' -i /etc/modprobe.d/l2tp_netlink-blacklist.conf
sudo sed -e '/blacklist l2tp_ppp/s/^b/#b/g' -i /etc/modprobe.d/l2tp_ppp-blacklist.conf
2 Likes
3

Thanks for the info, I’ll give it a shot. After looking into it some more it seems like they borked the connections manager in Fedora 36 somehow.