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EIGRP metric manipulation

EIGRP is the most complex metric between all routing protocols metrics, in this post we are trying to clear the calculation of this metric as much as possible. Lets begin.. EGIRP metric is a composite metric made up of 5 parameters listed as follows: Bandwidth. Delay. Load. Reliability. MTU. All these parameters are used to find the metric of the path by substitution in the the following formula: metric = [K1 * bandwidth + (K2 * bandwidth) / (256 – load) + K3 * delay] * [K5 / (reliability + K4)] Where K1 through K5 are constants that can be …

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EIGRP timers (hello, hold and active)

Today at work I have run into troubleshooting an EIGRP problem with one of our customers; while troubleshooting this problem I started making every optimization I know about EIGRP. In this post I am sharing with you EIGRP timers I adjusted in order to clear up the problem. Hello interval timer: Hello interval is the rate at which EIGRP sends hello packets. The command ip hello-interval eigrp can be used to set the hello interval time manually. Hello interval defaults to 60 seconds for low-speed, NBMA networks and 5 seconds for other types of networks. Hold timer: This is the …

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Passive-interface command behavior in RIP, EIGRP & OSPF

Passive-interface command is used in all routing protocols to disable sending updates out from a specific interface. However the command behavior varies from o­ne protocol to another. In RIP this command will disable sending multicast updates via a specific interface but will allow listening to incoming updates from other RIP speaking neighbors. This simply means that the router will still be able to receive updates o­n that passive interface and use them in the routing table. In EIGRP the passive-interface command stops sending outgoing hello packets, hence the router can not form any neighbor relationship via the passive interface. This …

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Automatic summarization in RIP and EIGRP

Summarization in RIP and EIGRP can be configured manually using the ip summary-address command or automatically using auto-summary command. when auto summarization is in effect routers behave as shown in the steps below: Subnets are summarized to their classful boundary before being sent to neighbors if they are not part of the major subnet of the exit interface. EIGRP automatically installs a discard route in the local routing table. RIP does not install a discard route by default. In the following example we will explore EIGRP with automatic summarization enabled: Router1 is connected to Router2 by a serial link and …

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