+.B l2tp_mtu
+MTU of interface for L2TP traffic (default: 1500). Used to set link
+MRU and adjust TCP MSS.
+.TP
+.B ppp_restart_time
+Restart timer for PPP protocol negotiation in seconds (default: 3).
+.TP
+.B ppp_max_configure
+Number of configure requests to send before giving up (default: 10).
+.TP
+.B ppp_max_failure
+Number of Configure-Nak requests to send before sending a
+Configure-Reject (default: 5).
+.TP
+.BR primary_dns ", " secondary_dns