So, in order for the global routing table to have EIGRP routes in it, EIGRP has to first be enabled, then go through a process through with it determines which routes are Feasible successors (Best routes) and only then install them to the global routing table.
EIGRP has five basic messages it uses for this EIGRP collaboration between its neighbors.
When EIGRP is up and operational, unicast and multicast EIGRP packets or constantly flooding the network to make sure EIGRP routes are up and are using the best path. These packets are important but not always necessary. There are situations when disabling an interfaces ability to spam the network with EIGRP packets is appropriate and will still allow for a fully operational EIGRP convergence. The way to achieve this is by configuring an interface to passive mode. EIGRP will still advertise the network/subnet configured on that interface, however, the interface will not participate in sending or processing of EIGPR packets.
Here is an example:
CCNP Routing & Switching ROUTE 300-101 Chapters 1 & 2 Notes:
Remote Site Connectivity:
- Multiprotocol Label Switching (MPLS) – is used by service providers and enterprise networks to segment traffic based on an MPLS label rather than an IP address.
- Tunnel-Based Virtual Private Networks
- Generic Routing Encapsulation (GRE)
- Dynamic Multipoint VPN (DMVPN)
- Multipoint GRE