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Knowledge base Mobile data L2TP handover

Our data SIMs allow for the possibility of L2TP hand over of mobile data to your own LNS. This means that the data SIM connects directly in to your network, and you control the IP address allocation, routing and any fire-walling or filtering you wish.


An L2TP tunnel is established using the pre-agreed IP addresses, hostname and shared secret. Note that if your LNS rejects the tunnel connection, or fails to respond to the SCCRQ or a subsequent HELLO, then it will be black listed for 5 minutes allowing further connections to go to the fall-back LNSs.

Once the tunnel is established, a session is established for each connecting data SIM.


Assigned Session ID14Session ID
Call Serial Number15Present if received from mobile network
Calling Number2219 digit ICCID of SIM, starting 8944


Framing Type19Always 1 (PPP)
Initial Received LCP CONFREQ26As received / negotiated by proxy
Last Sent LCP CONFREQ27As sent / negotiated by proxy
Last Received LCP CONFREQ28As received / negotiated by proxy
Proxy Authen Type29May be PAP or CHAP or may be absent if no authentication
Proxy Authen Name30User name from mobile device, typically blank
Proxy Authen Challenge31Chap challenge
Proxy Authen ID32Chap challenge ID
Proxy Authen Response33Chap response hash
Tx connect speed24Present if advised by mobile network
Rx connect speed38Present if advised by mobile network


  • Only available on data SIMs.
  • Called Number is a fixed APN and not the one entered on the phone, which is ignored.
  • Reduced MTU of 1450 is in operation when L2TP is run over the internet. This restriction can be removed to allow full 1500 byte MTU where direct baby-jumbo frame links are available from us to your LNS.
  • User-Name passed is what is provided by the mobile which is usually blank. Do not use the password 'password' as this may not be passed through.
  • IPv6 is not available yet, but is planned for the future if possible.