Which encapsulation is used when deploying EIGRP OTP?

While GRE is a common tunneling protocol, EIGRP OTP specifically integrates with and leverages LISP for its encapsulation and control plane mechanisms.

EIGRP OTP (Over the Top) is a Cisco feature designed to extend EIGRP routing across untrusted or non-EIGRP IP networks, such as the internet. It accomplishes this by using LISP (Locator/ID Separation Protocol) for encapsulation, which separates the identity of the endpoint from its current routing locator, enabling flexible overlay routing.

PPP is a data link layer protocol used for establishing direct connections between two nodes, not an encapsulation method for EIGRP OTP over an IP network.

802.1Q (dot1q) is a standard for VLAN tagging on Ethernet frames and is unrelated to the encapsulation used by EIGRP OTP.

MPLS (Multiprotocol Label Switching) is a forwarding mechanism that uses labels, but it is not the encapsulation technology specifically used by EIGRP OTP.

ISL (Inter-Switch Link) is a Cisco proprietary VLAN trunking protocol that has been largely superseded by 802.1Q and is not used for EIGRP OTP encapsulation.