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Know EIGRP in 2 Minute
EIGRP Routing Protocol
EIGRP (Enhanced Interior Gateway Routing Protocol) is a hybrid routing protocol. It has some characteristics from both the distance vector routing and the link-state routing.EIGRP Characteristics
• It is a Cisco proprietary. It only works on Cisco devices.• It is a classless routing protocol; this means that it supports the CIDR, the VLSM, and the discontiguous networks.
• The maximum hop count is ‘255’.
• It uses ‘DUAL’ (Diffusion Update Algorithm) to find the best path to the networks.
• It can load balance between up to six unequal cost paths.
• It uses the ‘successor route’ and the ‘feasible successor route’ for fast convergence.
• The ‘successor route’ is the route that is installed in the routing table in order to use it to reach a certain network.
• The feasible successor route can be considered as a backup for the successor route.
EIGRP Metrics
The default metrics used by the EIGRP protocol to calculate the path cost are the ‘delay’ and the ‘bandwidth’.However, the EIGRP protocol can use the delay, the bandwidth, the load, and the reliability as the path cost Metrics.
EIGRP Neighborship
The routers that are running EIGRP discover neighbors using the ‘hello’ messages.The routers must have the following conditions to form a neighborship,
i. The same AS number (Autonomous System number); the autonomous system is the network that exists under the same administration.
ii. The same path cost metrics.
ii. The same path cost metrics.
Only neighbors can exchange routes with each other using the multicast IP address ‘224.0.0.10’.
EIGRP Tables
Routers that are running EIGRP contain three tables,1. The neighbor table: it contains the EIGRP neighbors.
2. The topology table: it contains the ‘EIGRP topology, including the successor and the feasible successor routes.
3. The routing table: it contains the routes that are currently used to route the data.
EIGRP Configuration
To configure the EIGRP protocol on a router, we use the following commands,Router(config)# router eigrp AS number
Router(config-router)# network IP address wildcard mask
Router(config-router)# no auto-summary
