Skip to main content
Share Your Experience: Take the 2024 Developer Survey
10 votes

Configuring L2TP VPN to use with iOS 14 and macOS Big Sur

I was having this same problem after updating, change sha2-truncbug=yes > sha2-truncbug=no Using IPsec and xl2tpd for L2TP over IPsec server. The client is macOS Big Sur Version 11.0.1 ...
Joe's user avatar
  • 226
7 votes

Is there a speed and performance difference between VPNs (L2TP, etc.) vs. port forwarding?

Port forwarding would be quicker, but it would be less secure, in the sense that there is no confidentiality, or integrity. If you don't care then it is not a problem. Any VPN or tunnelling will add ...
SlyOne's user avatar
  • 363
5 votes

How do I bypass my VPN when making requests to IPs in my local network?

The solution was to modify the routing table in such a way that IPs in local network are routed via the default gateway: sudo ip route add via Where is the ...
Alexander Suraphel's user avatar
4 votes

Connected to Windows Server 2016 VPN on AWS but could not ping resources in VPC

Finally found the correct steps on how to create a VPN on Windows Server 2016 in AWS. Once connected, the client is able to access resources within the VPC and still access the Internet. Here's the ...
Carlo Miguel Cruz's user avatar
3 votes

How to veryify if VPN network encrypt data correctly in Windows 7?

Your "Local connection" is your regular (physical) connection over which the IPsec VPN tunnel is built. Disabling that interface will completely isolate your windows client from the network; thus the ...
Tommiie's user avatar
  • 5,675
2 votes

Simple L2TP/IPsec server not working (openswan, xl2tpd, Ubuntu, Windows)

I had similar problem. My server doesn't NAT, so this piece is not needed so removed it: conn L2TP-PSK-NAT rightsubnet=vhost:%priv also=L2TP-PSK-noNAT And when that's done NAT Traversel must be set ...
user66638's user avatar
  • 377
2 votes

Which ports for IPSEC/LT2P?

Okay. Actually - It depends. I have Ubuntu L2TP\IPSEC server behind NAT. if your L2TP\ipsec server sits behind NAT , in this case on your gateway (with NAT) you need to make port forward for the ...
Alex's user avatar
  • 318
2 votes

How to route traffic between L2TP/IPSec and WireGuard tunnels?

You need to add route on the L2TP VPN clients, which tells that packets to should be sent via Also, you need to add route on Wireguard server, which tells that packets to ...
Tero Kilkanen's user avatar
2 votes

Is there a speed and performance difference between VPNs (L2TP, etc.) vs. port forwarding?

I don't think you'd have a relevant performance gain for this specific example. Nonetheless, bear in mind a layer 2 to VPN would handle more traffic, like broadcasts, ARP packets, and NetBIOS packets. ...
surfingonthenet's user avatar
2 votes

Windows VPN client - how to make it connect to a different port?

Unfortunately, Windows VPN Client is not capable of changing the target TCP port of VPN connection. I would recommend you to setup a second IP address on your CentOS box and assign different xl2tpd ...
Net Runner's user avatar
  • 6,249
2 votes

Windows RRAS VPN failing to set options on Mac L2TP clients due to DHCP relay discarding packets

As it turns out, the defaults for the DHCP relay agent simply don't work for some L2TP clients. When you set up an interface for DHCP relaying in RRAS (on the "Internal" interface, where VPN ...
Shane Madden's user avatar
2 votes

Connection failed using L2TP on Ubuntu 20

A bit later I saw this. I had to adapt two more things: check box for “Enforce UDP encapsulation”. Uncheck all authentication methods except MSCHAPv2
Stefan Falk's user avatar
2 votes

The specified protocol identifier is not known to the router Windows server 2022

I've found one thread and one article online regarding this error message - both suggest the issue is IPv6 being disabled on the VPN server - have you checked for that? It seems like that prevents the ...
Argy Megalios's user avatar
1 vote

Difficulty setting up a cross-system docker network in NixOS

The answer turned out to be pretty simple once I figured out why systemd wasn't logging any errors, though I did go down the rabbit hole of figuring out why it kept showing the error L2TP tunnel with ...
FaerAnne's user avatar
1 vote

Windows 11 L2TP and IPSEC: Where to set the IpSec group

The only IPsec related Windows built-in VPN clients are: IPsec IKEv2 L2TP/IPsec Windows has no built-in IPsec IKEv1 Xauth (Cisco-style) VPN client. Some people recommend the Shrew Soft VPN Client ...
Douglas Kosovic's user avatar
1 vote

Connection failed using L2TP on Ubuntu 20

I had a similar problem using Ubuntu 22.04.2 LTS where the VPN configure refused to connect with the following error: starting l2tp dbus: failure: connect-failed (1) Setting "Enforce UDP ...
Cymon J. Cox's user avatar
1 vote

How to encode Pre-Shared Key (PSK) of and L2TP IPSEC connection managed by Network-Manager

libreswan and strongswan accept PSKs that are plain text or base64 starting with 0s. Similarily you can use either format in the vpn connection configuration file you want to edit. If you edit the ...
Douglas Kosovic's user avatar
1 vote

Diagnose L2TP VPN connection failures in CentOS 7

From the logs, IPsec phase 1 (main mode) is successful, but phase 2 (quick mode) failed. Perhaps the VPN server doesn't use Perfect Forward Secrecy (PFS) for phase 2 (quick mode). So try the "Disable ...
Douglas Kosovic's user avatar
1 vote

TP-LINK TL-MR6400 IPSEC L2TP VPN tunnel with GCP server

The solution you are trying to achieve is fine, just keep in mind that that workaround might increase your bandwidth and latency. As a side note, I am biased in favor of OpenWRT, but that firmware ...
Frank's user avatar
  • 381
1 vote

How to stop Windows Filtering Platform blocking ICMP packets for legitimate RDP traffic over L2TP tunnel?

The partial screen load before failure looks to me like a MTU size mismatch. It is common for tunnels to have a smaller MTU then 1500. As a test, temporarily reduce the configured MTU of your RDP ...
Guest's user avatar
  • 61
1 vote

VPN into router behind a Sonicwall

Make sure in the sonicwall, in the VPN user configuration, that those users are allowed to access the 192.168.100.X network. You did correctly by adding the firewall rules, but you have VPN policy ...
yagmoth555's user avatar
  • 17.2k
1 vote

strongSwan 5.6.2 and xl2tp 1.3.12 on Ubuntu 18.04 SA established but no traffic

There is a known bug in Linux kernel 4.15, which Ubuntu 18.04 ships, that causes the IP address to change in this way. It was caused by 5efec5c655dd ("xfrm: Fix eth_hdr(skb)->h_proto to reflect inner ...
ecdsa's user avatar
  • 4,102
1 vote

How to forward IPsec VPN with iptables

I recommend you do this eth0 is your "public interface" /sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE active routing /bin/echo 1 > /proc/sys/net/ipv4/ip_forward set nat to ...
asterissco's user avatar
1 vote

How do I get an L2TP Foxpass VPN connection working in Windows 10?

Windows defaults the L2TP connection to use CHAP, but you need to go into the adapter settings and switch it to PAP. That, along with the AssumeUDPEncapsulationContextOnSendRule, should get this ...
ArenS's user avatar
  • 36
1 vote

Configuring L2TP/IPSec on Cisco Router 2911

It seems you have a misconfiguration between yours hash algorithm : The conf of your router : ... crypto isakmp policy 20 encr 3des authentication pre-share group 2 hash md5 ... And ...
Sorcha's user avatar
  • 1,345
1 vote

L2TP client for Ubuntu

In 2018 you can use network-manager-l2tp - see my answer here for connecting to a Windows VPN server from Linux.
Stuart Cardall's user avatar
1 vote

Cisco IPSec Issue with Windows 10

Though I'm not sure that the VPN type was identical, when I got the error message The L2TP connection attempt failed because the security layer encountered a processing error during initial ...
kbulgrien's user avatar
  • 446
1 vote

I can connect, but cannot ping/route to remote VPN computers

After breaking my head over this the workarround was so easy. If the VPN client connects it get an IP from the main DHCP server than all network traffic is blocked. You must use a DHCP scope from the ...
BJ Computers's user avatar
1 vote

L2TP server allows connections through firewall for iPhone/iPad, but not windows

I've had this same problem, and it turned out that the local Windows firewall was blocking the connection. This guide helped me add the correct ports. Basically you need to open UDP Ports '50, 500, ...
privacychair's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible