On the WebUI, this is set under Tunnels, [[L2TP]], Incoming [[L2TP]] connections, and basic XML example is as below:
▲<gallery heightss=200px caption="Screenshots">
*pppdns1/2 - DNS servers that the FireBrick will give out
*lpc-rate/timeout - used for graphs - we don't need to poll as often as the actual LCPs are not answered by the SIM, but by the mobile network. Basically latency on the graphs for SIMs should be ignored.
The match settings are to match individual SIMs when the connect in, and thus giving them their own IP address etc.