Metric: Minimum bandwidth, delay, load, reliability, and maximum transmission unit (MTU).

Named EIGRP enables the configuration of EIGRP for both IPv4 and IPv6 under a single configuration mode.

Reliable Transport Protocol - The Reliable Transport Protocol (RTP) is unique to EIGRP and provides delivery of EIGRP packets to neighbors. RTP and the tracking of neighbor adjacencies set the stage for DUAL.

Equal and Unequal Cost Load Balancing - EIGRP supports equal cost load balancing and unequal cost load balancing, which allows administrators to better distribute traffic flow in their networks.

Establishing Neighbor Adjacencies - EIGRP establishes relationships with directly connected routers that are also enabled for EIGRP. Neighbor adjacencies are used to track the status of these neighbors.

Partial and Bounded Updates - The term partial means that the update only includes information about the route changes, such as a new link or a link becoming unavailable. The term bounded refers to the propagation of partial updates that are sent only to those routers that the changes affect. This minimizes the bandwidth that is required to send EIGRP updates.

Diffusing Update Algorithm - DUAL guarantees loop-free and backup paths throughout the routing domain. Using DUAL, EIGRP stores all available backup routes for destinations so that it can quickly adapt to alternate routes when necessary.

Acknowledgment packets - Used to acknowledge the receipt of an EIGRP message that was sent using reliable delivery.

Update packets - Propagates routing information to EIGRP neighbors.

Hello packets - Used for neighbor discovery and to maintain neighbor adjacencies.

Autonomous system number specifies the EIGRP routing process.

Fast convergence - It quickly propagates network changes

Scalable - It works well in small and large network sizes. Routers can be grouped into areas to support a hierarchical system.

Efficient - Routing changes trigger routing updates (no periodic updates). It uses the SPF algorithm to choose the best path.

Secure - OSPFv2 supports Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) authentication. OSPFv3 uses Internet Protocol Security (IPsec) to add authentication for OSPFv3 packets. When authentication is enabled, OSPF routers only accept encrypted routing updates from peers with the same pre-shared password.

Classless - OSPFv2 is classless by design; therefore, it supports IPv4 VLSM and CIDR.

Link-state request packet - Receiving routers can then request more information about any entry in the DBD by sending an LSR.

Link-state update packet - Used to reply to LSRs and to announce new information. LSUs contain seven different types of LSAs.

Database description packet - Contains an abbreviated list of the sending router’s LSDB and is used by receiving routers to check against the local LSDB

Link-state acknowledgment packet - When an LSU is received, the router sends an LSAck to confirm receipt of the LSU. The LSAck data field is empty.

Hello packet - Used to establish and maintain adjacency with other OSPF routers.