02-06-2013 03:21 AM - edited 03-04-2019 06:57 PM
Hi All,
While studying about EIGRP I found this diagram online & was confused by the description of how EIGRP chooses its best route...
Can some one please tell from the diagram, what would be the Advertised Distance, Reported Distance & Feasible Distance for the network 172.30.1.0/24 at R5 from each of R2, R3, & R4. Who would/wouldn't be the successors & feasible successors & why?
Thanks a lot in advance
Solved! Go to Solution.
02-06-2013 05:59 AM
Hello Pradeep,
In order to answer this question, you have to compute the resulting EIGRP metric from these component metrics, and compare the resulting numbers.
The formula to compute EIGRP metrics from individual components in default configuration is:
Metric = [ (10^7 DIV minBW) + Delay ] * 256
where DIV is an integer division (perform the normal division and take the integral part, throwing the fraction away).
So let's see:
Obviously, the path with BW=90, Delay=30 wins.
Best regards,
Peter
02-06-2013 03:28 AM
Just in case if the diagram is not clear:
R1 to R2 : BW=90 ; Delay=10
R1 to R3 : BW=100 ; Delay=10
R1 to R4 : BW=80 ; Delay=10
R2 to R5 : BW=100 ; Delay=10
R3 to R5 : BW=100 ; Delay=10
R4 to R5 : BW=100 ; Delay=10
02-06-2013 03:29 AM
Hello Pradeep,
Remember the following definitions:
So for R5, the distances would be:
Total distances must also take the links between R5 and R2/R3/R4 into account, i.e.:
The lowest total distance of R5 towards 172.30.1.0/24 will be through R3 which will initially also become the Feasible Distance.
Best regards,
Peter
02-06-2013 05:44 AM
Hi Peter,
Thanks for the reply. But If i have 3 different routes like this:
BW=90 Delay=30
BW=80 Delay=20
BW=70 Delay=10
which one is better? & why?
02-06-2013 05:59 AM
Hello Pradeep,
In order to answer this question, you have to compute the resulting EIGRP metric from these component metrics, and compare the resulting numbers.
The formula to compute EIGRP metrics from individual components in default configuration is:
Metric = [ (10^7 DIV minBW) + Delay ] * 256
where DIV is an integer division (perform the normal division and take the integral part, throwing the fraction away).
So let's see:
Obviously, the path with BW=90, Delay=30 wins.
Best regards,
Peter
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