-while :; do
- VPI=$(nvram get atm_vpi)
- VCI=$(nvram get atm_vci)
- USERNAME=$(nvram get ppp_username)
- PASSWORD=$(nvram get ppp_passwd)
- REDIAL=$(nvram get ppp_redialperiod)
- REDIAL=${REDIAL:+lcp-echo-interval $REDIAL}
- IDLETIME=$(nvram get ppp_idletime)
- IDLETIME=${IDLETIME:+lcp-echo-failure $IDLETIME}
- MTU=$(nvram get ppp_mtu)
- MTU=${MTU:-1492}
- MTU=${MTU:+ mtu $MTU mru $MTU}
+VPI=$(nvram get atm_vpi)
+VCI=$(nvram get atm_vci)
+USERNAME=$(nvram get ppp_username)
+PASSWORD=$(nvram get ppp_passwd)
+KEEPALIVE=$(nvram get ppp_redialperiod)
+KEEPALIVE=${KEEPALIVE:+lcp-echo-interval 1 lcp-echo-failure $KEEPALIVE}
+DEMAND=$(nvram get ppp_demand)
+case "$DEMAND" in
+ on|1|enabled)
+ DEMAND=$(nvram get ppp_idletime)
+ DEMAND=${IDLETIME:+demand idle $IDLETIME}
+ ;;
+ *) DEMAND="persist";;
+esac
+MTU=$(nvram get ppp_mtu)
+MTU=${MTU:-1500}