I am trying to find differences between PPPoE and L2TP.Both are tunneling protocols. When to use what?
The most and noticeable different is layer of tunneling.
PPPOE is a Layer 2 (Data Link Layer) tunneling protocol while
L2TP is a Layer 3 (Network Layer) tunneling protocol. This means that
PPPOE can create a tunnel between devices in a broadcast domain (such as devices connect to the same switch) but
L2TP can create a tunnel between two IP-based device anywhere in the world (if they are reachable from each other).
Suppose there are two computer A and B which are connected to a R:
A <------> R <--------> B
A cannot tunnels to B using
PPPOE because A and B are not in the same broadcast domain but a tunnel could be created using
Other differences are in authentication and encryption methods which
L2TP is more flexible in authentication and is more secure in encryption.