Experiment: Windows RRAS + Always on VPN + External DHCP

16/12/2025 admin News, Windows

To enable an external DHCP server run powershell command (admin mode):

reg add “HKLM\SYSTEM\CurrentControlSet\Services\Dhcp” /v RequiredPrivileges /d “SeChangeNotifyPrivilege”\0″SeCreateGlobalPrivilege”\0″SeImpersonatePrivilege”\0 /t REG_MULTI_SZ /f

Change RRAS settings to use an external DHCP server. Now it works.

I wanted to assign ip-addreses with an external DHCP server but it seems impossible.

In dhcpd.leases we can see:

lease 192.168.100.143 {
  starts 2 2025/12/16 14:28:44;
  ends 2 2025/12/16 16:28:44;
  tstp 2 2025/12/16 17:28:44;
  tsfp 2 2025/12/16 17:28:44;
  atsfp 2 2025/12/16 17:28:44;
  cltt 2 2025/12/16 14:28:44;
  binding state active;
  next binding state expired;
  hardware ethernet 00:0c:29:ca:c5:39;
  uid "\001RAS \000\014)\312\3059\000\000\006\000\000\000";
  set vendor-class-identifier = "MSFT 5.0";
  client-hostname "RRAS-Server";

I tried to use this construction but it is useless:

class "specific-client" {
    match if option host-name = "my-device-name";
}

pool {
    allow members of "specific-client";
    range 192.168.1.50 192.168.1.50;  # Assigns a single fixed IP
}

A hardware ethernet and a uid are always the same: RRAS-Server’s.

RRAS-server occupies a lot of ip-addresses on an external DHCP-server for all the connectors.

So, it was useless and I fall back to the internal RRAS DHCP-server.

Check a checksum for HP ISO