4.1.c [iii] LISP encapsulation principles supporting EIGRP OTP
EIGRP Over the Top (OTP) allows the customer to establish EIGRP adjacencies across the MPLS/ VPN provider cloud. An EIGRP targeted adjacency between CEs is created. This EIGRP neighborship is done via unicast packets, using the CE ‘WAN’ IP address. This “over the top” peering allows EIGRP to exchange customer prefixes directly between CEs. Customer prefixes are NOT injected in the providers VRF routing table. In order to allow for proper forwarding of user traffic across the MPLS/ VPN cloud , user packets are encapsulated on the CE. The encapsulation header uses the WAN IP address of the CEs, which are known in the MPLS/ VPN cloud.
OTP control plane consists in an EIGRP targeted adjacency between CEs.
Neighborship is established using the CE WAN address, i.e. address of CE on the PE/ CE link, so there is no need for any dynamic routing protocol between the PE/ CE. The PE just needs to redistribute the connected routes.
Since the customer prefixes are not known in the VRF of provider, customer traffic can’t be natively forwarded through the provider cloud, but needs to be encapsulated by CEs before being sent through the provider cloud.
OTP leverages existing LISP encapsulation which:
● Allows dynamic multi-point tunneling
● Provides instance ID field to optionally support virtualization across WAN (see EVN WAN Extension section)
OTP does not use LISP control plane (map server/ resolver, etc.) instead it uses EIGRP to exchange routes and provide the next-hop, which LISP encapsulation uses to reach remote prefixes.
Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4478-4488). . Kindle Edition.