topic Re: CP1575 L2TP VPN Remote Access in Spark Firewall (SMB)

CP1575 L2TP VPN Remote Access

PavelSpiridonov — Tue, 24 Feb 2026 09:01:28 GMT

Hello!

When attempting to establish an L2TP VPN connection between the CP1575 and a third-party router (Mikrotik),
an error occurs: 'IKE failure: Quick Mode New DH key received during Quick Mode from peer, but Perfect Forward Secrecy is not set in the community.'
However, the standard Windows L2TP client successfully connects to the CP1575.

This issue has already been discussed, but in that case, the client was Linux.

Unfortunately, the Linux solution isn't applicable in my case:
the Mikrotik L2TP client doesn't have an option to affect the PFS parameter.

I noticed that the CP1575 has an 'Enable PFS' setting.
However, it's only available under 'Site to Site VPN'.
Is it possible to find such a setting for L2TP VPN?
Perhaps it can be found through the Gaia Clish?

Re: CP1575 L2TP VPN Remote Access

PhoneBoy — Tue, 24 Feb 2026 23:42:47 GMT

You can try to do the following two in Expert mode:

ckp_regedit -a \\SOFTWARE\\CheckPoint\\VPN1 force_ra_pfs -n 1
fw_configload

These steps are similar to what's in the Remote Access VPN on non-Spark gateways: https://sc1.checkpoint.com/documents/R82/WebAdminGuides/EN/CP_R82_RemoteAccessVPN_AdminGuide/Content/Topics-VPNRG/Remote-Access-Advanced-Configuration.htm#Perfect_Forward_Secrecy_(PFS)
The second step is the "install security policy" step.

Re: CP1575 L2TP VPN Remote Access

PavelSpiridonov — Sat, 28 Feb 2026 13:31:34 GMT

The connection was established successfully,
your advice helped.

The following restrictions apply:
the 'IP address for Office Mode' parameter must be set in the Remote Access Users.
Authorization algorithm - only SHA1
PFS Group - only modp1024

I tried to influence the PFS Group using the parameter,
\\SOFTWARE\\CheckPoint\\VPN1 users_hash_capacity
replacing the value with 2048,
but to no avail — the connection was don't established.

Can you tell me how to correctly configure the authorization algorithm and PFS Group parameters?

Re: CP1575 L2TP VPN Remote Access

PhoneBoy — Mon, 02 Mar 2026 17:41:12 GMT

Not sure it is possible to do that, unfortunately.
Suggest consulting with TAC.