EIGRP (Enhanced Interior Gateway Routing Protocol) and OSPF (Open Shortest Path First) are both interior gateway protocols used for routing within a single routing domain. Let's compare their metrics and administrative distances:
* Metrics:
* EIGRP Metrics:
* EIGRP uses a composite metric called "feasible distance" to determine the best path to a destination.
* The EIGRP metric is based on a combination of several factors, including bandwidth, delay, reliability, load, and MTU (Maximum Transmission Unit).
* EIGRP calculates the metric using a formula that takes into account these parameters.
* The metric is used to select the best route among multiple paths to the same destination.
* OSPF Metrics:
* OSPF uses a simple metric called "cost" to determine the best path.
* The cost is based solely on the interface bandwidth.
* OSPF routers calculate the cost by dividing a reference bandwidth (default is 100 Mbps) by the actual link bandwidth.
* The path with the lowest cost is chosen as the best path to reach the destination.
* Administrative Distances:
* EIGRP Administrative Distance:
* Administrative distance (AD) is a value assigned to each routing protocol to indicate its trustworthiness.
* For external routes (routes learned from other autonomous systems), EIGRP assigns an AD of 170.
* OSPF Administrative Distance:
* OSPF does not use administrative distances in the same way as EIGRP.
* OSPF relies on the cost metric to determine the best path.
* The administrative distance for external routes in OSPF is undefined because OSPF does not directly use AD for route selection.
In summary, EIGRP uses a more complex metric based on multiple factors, while OSPF uses a simpler metric based solely on interface bandwidth. Additionally, OSPF does not explicitly define an administrative distance for external routes.
References:
* Cisco Enterprise Networking Planet: 1
* Cisco Community: 2
* PyNet Labs: 3
* Catchpoint: