DUplicate encryption setting for L2TP + IPsec

RouterOS General
1

I have setup an L2TP+IPsec tunnel between sites. In PPP > Profiles I have created a profile for the tunnel which has “Use Encryption” set to yes.

in the PPP > Interface > L2TP settings I have Use IPsec = required.

Since IPsec does encryption, does the above settings mean that L2TP is also doing encryption? If not, what is the Use Encryption setting for in the PPP Profile?

2

It activates MPPE (Microsoft Point-to-Point Encryption), and indeed you can use the /ppp profile with no use-encryption=no if you protect L2TP using IPsec. MPPE is not considered secure enough these days so it doesn’t provide any security enhancement if used in addition to IPsec.