eigrp cost calculation

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Sep 25th, 2010
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sir,

i have a 2 no of router which is connected with back to back. Bandwidth of one serial is 512 Kbps and another is 2048, eigrp rouiting protocol is running between two router. i want to know, when eigrp calculate cost which bandwidth it will take and why?

and requesting u to provide me some link related with this type of scenario


Thanks

tirthasarathi

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Jon Marshall Sat, 09/25/2010 - 04:02
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tirthasarathi.datta wrote:


sir,

i have a 2 no of router which is connected with back to back. Bandwidth of one serial is 512 Kbps and another is 2048, eigrp rouiting protocol is running between two router. i want to know, when eigrp calculate cost which bandwidth it will take and why?

and requesting u to provide me some link related with this type of scenario


Thanks

tirthasarathi


EIGRP uses bandwidth and delay by default although it can use another 3 metrics as well. Note Cisco recommned not to use the other 3 metrics.


The simple answer to your question is it will use the 2048 link providing you have configured the bandwidth correctly under the interface. See this link for a full explanation -


EIGRP metrics


Jon

tirthasarathi.datta Sun, 09/26/2010 - 09:49
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Thanks for reply. Whatever u say thats i know. But my question was different. In that scenarion only, which bandwidth eigrp use for bandwidth calculation.


Router A ( 64 K)


Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D       10.0.0.0/8 is a summary, 00:04:13, Null0
C       10.0.0.0/30 is directly connected, Serial0/0/0
C    192.168.20.0/24 is directly connected, Loopback0
D    192.168.30.0/24 [90/40640000] via 10.0.0.2, 00:04:10, Serial0/0/0



Router B (2048 K)



Gateway of last resort is not set

     10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
D       10.0.0.0/8 is a summary, 00:01:18, Null0
C       10.0.0.0/30 is directly connected, Serial0/0/0
D    192.168.20.0/24 [90/1889792] via 10.0.0.1, 00:01:14, Serial0/0/0
C    192.168.30.0/24 is directly connected, Loopback0


(delay is same in both router)


Thanks

tirthasarathi

Jon Marshall Sun, 09/26/2010 - 09:56
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Not sure what you mean.


Router A will use the 64K bandwidth value in it's calculations to get to networks on B and B will use 2048K in it's calcluations to get to A. EIGRP uses the minimum bandwidth configured on the path to a destination network. As you only have 2 routers A will use it's bandwidth value to get to B and B will use it's bandwidth value to get to A.


Jon

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