Bandwidth under the gig interface

Unanswered Question

HI Experts

if i have a link(300M) runing on the gig interface(int g0/1)do i need to configure the actual Bandwith in gig interface?


interface g0/1

Bandwidth 300

waht does the effect if i didn't configure the Bandwidth under the gig interface



I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (2 ratings)
mheusinger Wed, 02/14/2007 - 05:14


the bandwidth statement influences mainly two things: IP routing metric and QoS behaviour.

1) IP routing

From the configured bandwidth some protocols like OSPF or EIGRP deduce routing metric. EIGRP, which you are using, will in fact take the minimum bandwidth along the path. So it only matters if for some networks the lowest bandwidth is above 300 Mbps.

By the way the proper interface command will be "bandwidth 300000" as the value is in kbps!

2) QoS

bandwidth will influence allocated bandwidth in CBWFQ, if configured based on percentages. In your case, as far as I understand, The SP limits the Gig to 300 Mbps. It then is required to configure nested policies, if you want to implement QoS on this interface. Have f.e. a look at "QoS Child Service Policy for Priority Class"

So I would always set the bandwidth parameter according to the maximum traffic throughput possible, regardless of physical interface speeds.

Hope this helps!

Regards, Martin

royalblues Wed, 02/14/2007 - 05:21


You should configure the exact bandwidth statement under the interface when you are using a routing protocol like OSPF & EIGRP as these use it to calculate the metric.

In your case EIGRP will see it as a 1 GIG link & as you know EIGRP can use 50% of the bandwidth for its routing updates unless configured otherwise.

So it is always advisable to configure the correct bandwidth under the interface

HTH, rate if it does



This Discussion