How to calculate bandwidth for logical interface (Vlan interface) ?

[srinivas_patnaik]

Hello Community Members
I am facing issue in my client network where  interface utilization alerts are received for  interface Vlan 500 (SVI) on Nexus 5K Switch causing high volume of alert incidents triggered from monitoring tool. When analysed, it was identified that the backup activity is causing the issue. Default bandwidth is defined on interface vlan 500.  Below is the output from " show interface vlan 500" 

FACN5KSW001# show interface vlan500 

Vlan500 is up, line protocol is up
Hardware is EtherSVI, address is 00de.fb55.d8c1
Description: *****Services*****
Internet Address is 10.64.5.2/24
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec

Aroud 15 physical ports of each 40Gig is associated with the vlan 500. I am planning to increase the interface vlan 500 bandwidth from default 1Gbps.  If i have to increase the bandwidth on  interface vlan 500, is there a standard bacndwidth calculation based on which i can conclude what bandwidth need to configure so that auto alerts are minimised. 

Thank you for your support

[balaji.bandi]

Default of VLAN is 1GB as you mentioned, you do not like alert then increase the bandwidth on the interface.

but if this interface part of any IGP - it may changed based on the cost path calculated.

any way its virtual so increase to 1-10GB (any number is works for you)

[srinivas_patnaik]

Hi Balaji 
Even i have the same undertsanding.  If i propose to increse the bandwidth to 10Gps , What justifiction to be provided  fo the same. 

[liviu.gheorghe]

Hello @srinivas_patnaik ,

the bandwidth parameter on an interface is used traditionally by routing protocols to derive the metric - OSPF, EIGRP. Other use cases are, like you mentioned, Network Management Applications that read the bandwidth parameter and alerts you when a certain threshold is passed.

The maximum value that can be configured on a Vlan interface is 200000000 kbps which is almost 200 Gbps. 

In your case, given that you have 15 interfaces of 40 Gbps, you could surpase the 200 Gbps maximum configurable bandwidth very easy. In my opinion, I thing it would be best to exclude the Vlan 500 from the "alerting list" in your Network Management Application.

Hope this helps.

[Joseph W. Doherty]

Does your monitoring tool show peak bandwidth usage?  If so, set bandwidth value somewhere between that and 100% of possible usage.  Basically, as already suggested in another reply, whatever value you want to alert on.

As also noted in another reply, the bandwidth statement appears incapable of being set to the actual possible SVI bandwidth usage, in your case.  Either exclude SVI, as was also suggested, or contact your network monitoring software vendor and see if a maximum bandwidth value can be set in software without using device's interface bandwidth value.