Mikrotik L2TP/IPSec Firewall Rule Set

/ip firewall filter
add action=accept chain=input in-interface=ether1 protocol=ipsec-esp
comment="allow L2TP VPN (ipsec-esp)"
add action=accept chain=input dst-port=1701 in-interface=ether1 protocol=udp
comment="allow L2TP VPN (1701/udp)"
add action=accept chain=input dst-port=4500 in-interface=ether1 protocol=udp
comment="allow L2TP VPN (4500/udp)"
add action=accept chain=input dst-port=500 in-interface=ether1 protocol=udp
comment="allow L2TP VPN (500/udp)"