Blog
EIGRP automatic summarization
Route summarization is the most common tuning methods of EIGRP. It allows a router to group multiple networks and advertises them as one large group using a single, summarized route. The capability to summarize routes is very important due to the rapid growth of networks. Route summarization reduces the number of routes in the larger […]
Topology Table
The EIGRP topology table contains all of the information about all known routes received from EIGRP neighbors. As an EIGRP router learns routes from its neighbors, those routes are stored in its EIGRP topology table. If a neighbor is advertising a possible route, it has to be using that route to forward packets to the destination network. The topology […]
Successor, Feasible Successor and Feasible Distance
Successor -A successor route is the best route to a destination network. EIGRP uses the successor route to forward traffic to a destination. This is the router which is stored in the routing table. A successor route is based on the advertised distance from the neighbor. A successor route is a least-cost route to the […]
Introduction to DUAL
The diffusing update algorithm (DUAL) is the algorithm used by EIGRP routing protocol to make sure that a given route is recalculated globally whenever it might cause a routing loop. It is guarantees loop-free and backup paths throughout the routing domain. EIGRP store all available backup routes using diffusing update algorithm and then adapt the […]
How to Calculate EIGRP Metric
EIGRP automatically calculates the routing table metric to choose the best path. But it is important that the network administrator understands how to calculate EIGRP metric. The default formula for the composite metric is: [k1 x Bandwidth + k3 x delay] x 256 By default K1 and K3 is equal to 1 so the formula […]
Delay Metric
Delay Metric is the measure of the time it takes a bit to be transmitted to an adjacent neighbor. The delay metric (DLY) is a constant value based on the type of link to which the interface is connected. The value is expressed in microseconds, the one-millionth of a second. In the EIGRP metric calculation, […]
Bandwidth Metric
EIGRP and OSPF both are using bandwidth metric which is a static value for calculating routing metric. The bandwidth is displayed in kilobits per second (kb/s). The default bandwidths for different interfaces are: Serial Interface – 1544 kb/s Ethernet is – 10,000 kb/s FastEthernet – 100,000 GigaEthernet – 1,000,000 TenGig – 10,000,000 Figure 1 illustrates […]
EIGRP Composite Metric
A composite metric is a number calculated based on several different components that determine the preferred route. By default, EIGRP uses bandwidth and delay to calculate the preferred path to a network. The reliability and load can also be used, but are not recommended, because they typically result in a frequent recalculation of the topology […]
EIGRP Topology Table
EIGRP uses a neighbor table, topology table, and IP routing table. The neighbor table maintains a state of neighbors. The topology table is used to store information about all known routes received from all neighbors. EIGRP Update messages send the routers’ EIGRP topology tables. The EIGRP topology table is a database of possible routes. Each […]
