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Webcast-Catalyst9k
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Question on EIGRP

Hi,

We have two 2821 routers in two different locations. Both these locations are communicating using leasedline. and the propotal using is EIGRP.

Now we got a framerelay link at both these locations and we are planing to keep this link as a backup link.

Now my requirement is

EIGRP has to select the leased line link as successor.

EIGRP decide which link is successor and feasible successor depending on its own parameter calculations.

Parameters include Bandwidth, Delay, Load, Metric, Reliability, and Advertise Distance.

Can someone please provide me the configuration steps for the same.

4 REPLIES

Re: Question on EIGRP

Hi Chaitu,

By default EIGRP uses only Bandwidth and Delay in its metric calculations.

It is not recommended to change this, though it is possible.

You should build up the neighbor relationship over the frame relay link between the two 2811 routers. You will then have 2 neighbor relationships: one through the leased line, another through the frame relay link.

Then you can play around with the Bandwidth and Delay settings of the interfaces to make the leased line more preferable for EIGRP.

Example:

interface s1/0

bandwidth xxx (in kbits/sec)

delay yyy (in microseconds)

This will change the metric of routes over the serial interface and you should use a setting that will make the metric less than the metric over the frame relay link.

You should set the metric on both sides of the link so the traffic is sent over the leased line interfaces in both directions.

Be aware that changing the bandwidth setting of the interface will have effect on the QoS operations if you have QoS configured on the interfaces.

Therefore, if QoS is configured, it is better to change the Delay parameter.

Cheers:

Istvan

Cisco Employee

Re: Question on EIGRP

Hi Istvan,

Very nice answer indeed! Let me add one more comment. As a general recommendation, the bandwidth command should never be used to manually influence the EIGRP metric and make one route more preferred than some other. The EIGRP is allowed to reserve by default up to 50% of the interface bandwidth for its own traffic. If the bandwidth on an interface is set to a higher value than the real speed of the interface, the EIGRP may begin monopolizing the interface or even saturating it with its own traffic. Therefore, it is always recommended to set up the bandwidth command to the real information-carrying capacity of the interface, and if further EIGRP metric manipulations are necessary, the delay command should be used for that purpose.

Best regards,

Peter

Re: Question on EIGRP

Thank you for your contribution Peter!

You deserve a good rating for that.

Cheers:

Istvan

Cisco Employee

Re: Question on EIGRP

Istvan,

Thank you very much - I am honored by your compliment!

Best regards,

Peter

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