EIGRP Bandwidth Calculation

adam-b

Hey Guys, here is a question that in my opinion is not covered very well in the BSCI Study Guide.

When calculating feasible distance, does EIGRP use the bandwidth and delay as configured on the local outbound interface or on the next hop's inbound interface? I have read mixed things on this and was not able to spend enough time today in the lab to make a definite determination. I figured this would be a good point to clarify as it is pretty fundamental.

My best answer is that the router will use the delay as configured on the next hop inbound interface and the bandwidth as configured locally. What do you guys say?

Thanks for the discussion.

-Adam

rakem

I believe it is the local outbound interface. As changing the bandwidth configuration on the interface should change the feasible distance.

dtlokee

It should use the attributes of the local interface the EIGRP update was received on. Using bandwidth to modify the EIGRP metric can be misleading since the DUAL algorithm only considers the lowest bandwidth along the path. If you change the bandwidth of the interface from 1000000 to 100000 but there is a T1 along the path with it's bandwidth set to 1544 then that change will not affect the metric.

adam-b

thanks for your replies guys!

dtlokee: good point about minimum bandwidth.