Answers: Basic EIGRP

By Wendell January 27, 2016 09:05

Configure EIGRP, and configure the link delay – and influence the routes in a small lab network. That’s the summary of your task for this most recent lab. Check out the original lab post first, create your own answer, and then come back here to check your answer.


Figure 1: Router Triangle with IP Subnets (EIGRP I – 2.jpg)


Example 4: R1 Config


Example 5: R2 Config


Example 6: R3 Config



First, none of the routers had EIGRP configured yet, so the configuration on all three routers enables EIGRP. In this case, all three routers use the same configuration. All use ASN 5 as requested (router eigrp 5), and all use the network command, which enables EIGRP on all interfaces with addresses in class C network (which includes all interfaces in the figure).

EIGRP uses the worst (slowest) bandwidth in the metric calculation for each competing route. In this lab, all the links have a bandwidth of 1 Gbps (a literal setting of 1,000,000, meaning 1,000,000 Kbps). As a result, all the alternate routes use the same minimum bandwidth, so the bandwidth has no impact on a router’s choice of best (lowest) metric.

EIGRP uses delay by adding the delay for each link in a route; in other words, EIGRP uses the cumulative delay, rather than the worst delay among all links in the route. Gigabit interfaces (when running at Gigabit speed) default to a 10 microsecond delay. By configuring both R2 ad R3 to use a much higher delay setting on the link between these two routers, in this case, all the routers will prefer routes through R1, rather than routes that use the R2-R3 link.

Also, note that the interface delay subcommand uses a unit of 10’s of microseconds, so the correct command in this case is delay 100, which equates to 1000 microseconds.

IPv6 Addressing with OSPFv3 - 2
EIGRP and Delay
By Wendell January 27, 2016 09:05
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  1. Ruben May 15, 16:11

    Hello Wendell!
    A quick question related to this exercise: When forcing the delay to 1000 microsecs like in this exercise, does this mean that both R2s G0/1 and R3s G0/2 need to have the subinterface command ‘speed 10’ configured?
    I’m guessing no, because if someone came and forced that link to a 10Mb speed, EIGRP would automatically sense it and adjust the metric by itself immediately, correct?

    Reply to this comment
    • Gabriel October 3, 00:25

      You do not have to, as the bandwidth/delay setting is only used for the EIGRP metric calculation. Not actual speeds.

      Reply to this comment
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