OSPF Path Cost & Influences

OSPF metric is cost. It chooses a path based on the lowest cost to that destination. Link bandwidths on outgoing interfaces to a destination accumulate and give us a cost to that destination. It is possible to manipulate link costs directly or by changing the bandwidth of the interface itself. Of course, changing the bandwidth of a link is solely for route calculation here and does not actually affect the physical speed of the link itself.

EIGRP Initialization

There is classic mode EIGRP (unnamed) and named mode EIGRP. Named mode offers a lot of convenience compared to the traditional method of setting up the protocol.

EIGRP Convergence, Optimization, and Scalability

 

Convergence timers, query scoping with summarization, query scoping with stub routing, stub routing with a leak map, bandwidth pacing, and graceful restart, all work together or separately to improve network performance by reducing updates, creating smaller route tables, and limiting the amount of control plane traffic, while maintaining effective end-to-end connectivity.

EIGRP Path Selection

By default, EIGRP uses bandwidth and delay to calculate metric. EIGRP feasibility, vector attributes, metrics, metric weight, and load balancing.

EIGRP Summarization & Leak Map

Longest match routes in the table are preferred. However summarizing tables will reduce the size in terms of bytes, visually, and the lookup time of a route for a packet.

EIGRP Metric Influence: Offset Lists, AD

Instead of playing around with EIGRP bandwidth and delay to influence route selection, we can use something more reliable, more stable to do just that: offset lists. We may use offset lists to prefer one path over another, or create an “equal cost load balance” solution.

EIGRP Filtering: Prefix & Distribute-List

EIGRP Route Filtering

 

The following is an example of EIGRP route filtering between two peers through the usage of a prefix list and a distribute list. This quick tutorial will show how to eliminate unwanted routes from a route table and effectively reduce the size of the table visually and in terms of memory and processor time.

EIGRP Authentication

Protocol authentication ensures that the authenticated neighbor is most likely the neighbor intended. Authentication allows peers to verify one another and prevents any rogue routers from being added to the topology because it does not have the associated key chain or passphrase.