EIGRP is sometimes referred to as a hybrid routing protocol or an advanced distance vector protocol because is has characteristics of both distance-vector some link-state protocols. For example, EIGRP doesn't send link-state packets like OSPF does. instead, it traditional distance-vector updates that include information about networks plus the cost o reaching them from the perspective of the advertising router.
EIGRP has link-state characteristics as well it synchronize network topology information between neighbors at startup and then sends specific updates only when topology change occur.
EIGRP has a default hop count of 100, with maximum of 255. In EIGRP speak, hop count refers to how many router an EIGRP update packet can go through before it will be discarded, which limits the size of the autonomous system (AS).
Here's a list of some powerful features:
- Support for IP and IPv6
- Considered classless
- Support for VLSM/CIDR
- Support for summaries and discontinuous networks
- Efficient neighbor discovery
- Communication via Reliable Transport Protocol (RTP)
- Best path selection via diffusing Update Algorithm (DUAL)
- Reduced bandwidth usage with bounded updates
- No broadcast
- Hello and Acknowledge received
- Autonomous System (AS) numbers match
- Identical metrics (K values)