RouterOS v6.44 or above: https://saputra.org/threads/mikrotik-l2tp-over-ipsec-vpn-server-tutorial-guide-for-routeros-v6-44.106/

Stats: http://rickfreyconsulting.com/mikrotik-vpns/

New info? http://wiki.mikrotik.com/wiki/Manual:IP/IPsec#Road_Warrior_setup_with_Mode_Conf

Needs verification and completion

http://wiki.mikrotik.com/wiki/Manual:Interface/L2TP#Server_configuration

http://wiki.mikrotik.com/wiki/Manual:Interface/L2TP

https://www.youtube.com/watch?v=tpgEqzwj_OQ

• All traffic routes through tunnel

PPP → Interface → L2TP Server → Enable

• Max MTU
  • L2TP has 40-byte overhead
  • 1450 - Lowering the MTU can speed up VPN - test path MTU first
  • 1460 - Default - Good if uplink MTU is 1500
• Default Profile
  • Select default-encryption or create your own profile
• Authentication
  • De-select chap and pap
  • Select MSCHAPv2 and MSCHAP1
• Select Use IPsec
• Enter IPsec Secret needed to configure client
• Click OK

IP → Pool → Add

• Name L2TPpool
• Range of addresses e.g. (192.168.1.10-192.168.1.20) outside of LAN DHCP range

PPP → Profiles → Default-Encryption

• Local Address (same for all)
• Remote Address (pool you created)

PPP → Interface → L2TP Server

• Specify Default Profile → default-encryption

PPP → Secrets → Add+

• Name
  • Username
• Password
• Service
  • l2tp
• Local Address (leave blank if using IP pool)
  • Same for all users
  • Router's LAN address
• Remote Address (leave blank if using IP pool)
  • Different for each user
  • Outside of DHCP range
• Profile
  • default-encryption

Enable Proxy-ARP on the LAN interface for proper (layer 2 address) ARP resolution.

If you use a LAN bridge, modify that.

Interfaces → etherN → General → ARP → Proxy-ARP