Friday 10 September 2010

BSCI - EIGRP - Metric Weights

When redistributing another routing protocol in to EIGRP you need to specify the metric weights in order to redistribute the routes correctly and efficiently.

The command you need to perform redistribution is:
R1(config)#router eigrp 1
R1(config-router)#redistribute ospf 1 metric 1500 10 255 10 1500

Alternatively you can define a 'Seed' metric which is applied to all redistributed routes and so you don't need to specify the individual metrics each time.

R1(config)#router eigrp 1
R1(config-router)#default-metric 1000 100 250 100 1500
R1(config-router)#redistribute ospf 1

The values stated above represent each of the values for the EIGRP metric:
R1(config-router)#default-metric bandwidth delay reliability loading mtu 

In both of the examples above you are manually setting out the metric for the routes once they are redistributed in to EIGRP.

If you fail to set either a default metric or a specific metric in your redistribute command then EIGRP will assign a metric of 'infinity' and the routes will fail. So if you end up scratching you head wondering why your desired routes don't appear in the routing table take a look at your metrics.

The metric set out above represent the K-values for each of the criteria that make up the EIGRP Metric. The K values are:
i) Bandwidth (K1) - Minimum bandwidth along the path in Kbps. This is a value of 1 - 4294967295
ii) Load (K2) - Used as a way of managing traffic off heavily used links. Value is 0 to 255 where 255 equals is 100% utilisation of the available bandwidth
iii) Delay (K3) - Latency of the path in 10's of Microseconds. This is a value of 1 - 4294967295
iv) Reliability (K4) - A value representing how likely the path is to be available or fail. Value is between 0 and 255, with 255 equalling 100% reliable.
v) MTU (K5)- Used to set a path MTU for a given route. Value is 1 - 65535

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