EIGRP summary

Here is a list of the most important EIGRP features:advanced distance vector routing protocolclassless routing protocolsupports VLSM (Variable Length Subnet Mask)converges fastsupports multiple Network layer protocols (IPv4, IPv6, IPX, AppleTalk…)uses multicast address of for routing updatessends partial routing updatessupports equal and unequal-cost load balancingsupports manual summarization on any router within a networkby default, uses bandwidth and delay to calculate its metricCisco Read more [...]

EIGRP Diffusing Update Algorithm (DUAL)

Diffusing Update Algorithm (DUAL)┬áis an algorithm used by EIGRP to select and maintain the best route to each remote network. DUAL is also used for the following purposes:discover a backup route if there is one available.support for variable length subnet masks (VLSMs).perform dynamic route recoveries.query neighbors for unknown alternate routes.send out queries for alternate routes. EIGRP stores all routes advertised by all EIGRP neighbors. The metric of these routes is used by DUAL to select Read more [...]

EIGRP Reliable Transport Protocol (RTP)

EIGRP doesn’t send messages with UDP or TCP; instead, a Cisco’s protocol called Reliable Transport Protocol (RTP) is used for communication between EIGRP-speaking routers. As the name implies, reliability is a key feature of this protocol, and it is designed to enable quick delivery of updates and tracking of data reception.Five different packets types are used by EIGRP:Update – contains route information. When routing updates are sent in response to the metric or topology changes, Read more [...]

EIGRP authentication & load balancing

EIGRP authenticationEIGRP authentication is used to prevent an attacker from forming the EIGRP neighbor relationship with your router and advertising incorrect routing information. By using the same preshared key (PSK) on all routers you can force EIGRP to authenticate each EIGRP message. That way you can ensure that your router accepts routing updates only from the trusted sources. To authenticate every message, the MD5 (Message Digest 5) algorithm is used.Three steps are required to configure EIGRP Read more [...]

EIGRP automatic & manual summarization

Route summarization is a method of representing multiple networks with a single summary address. It is often use in large networks with many subnets because it reduces the number of routes that a router must maintain and minimizes the traffic used for routing updates. Two methods for summarizing routes exist: automatic summarization and manual summarization.EIGRP automatic summarizationBy default, EIGRP has the auto summary feature enabled. Because of this, routes are summarized to classful address Read more [...]

Wildcard mask in EIGRP

The network command in EIGRP uses a classful network as the parameter by default, which means that all interfaces inside the classful network will participate in the EIGRP process. We can enable EIGRP only for specific networks using wildcard masks. The syntax of the command is:(router-eigrp)#network IP_ADDRESS WILDCARD_MASKWe will use the following example network:The router is directly connected to three subnets. Let’s say that we want to advertise only the subnet in EIGRP. We Read more [...]