Cisco Nexus not support SNMP vlan traffic

[udiya]

Hello,
I understand that cisco-nexsus products do not support vlan traffic measurement via SNMP ,
There is an alternative way to do it ? sflow? netflow ?

Thanks
Udi

[riversdev0]

Cisco Nexus switches forward layer 2 frames (called "switching") and layer 3 packets (called "routing") in hardware, not in software. Both the vlan and the vlan interface (called an "SVI") are methods for programming the hardware, not method for funneling traffic through a particular software feature (like routing). This means that there is no single counter that measures traffic going through a vlan or vlan interface, because each physical interface ASIC is performing the function of the vlan or the vlan interface in a distributed, autonomous, manor.

Additionally, most (maybe all) Nexus switches are non-blocking, which means they can support line-rate traffic through all ports simultaneously (provided that no individual port exceeds its physical limits of 1Gig/10Gig/40Gig, etc). Therefore, if there did exist a counter for vlan traffic, and if you were to graph that counter in Cacti, it would very well exceed normal Ethernet speeds. The amount of traffic a vlan or vlan interface can carry is only limited by the physical ports in the chassis. Therefore, you will never be in danger of reaching a vlan limit without already reaching a physical limit on one or more ports.

NetFlow is a way of generating metadata about traffic flowing through a network device. That data is not merely numbers, it is sources and destinations, and other protocol information. Therefore, you need a system that can store and perform math upon that metadata in order to produce a graph. That is the main reason why good NetFlow analyzers are normally very costly. That is not what Cacti, nor rrdtool, was intended to do.

Ultimately, I don't think you can get the traffic measurement that you want from a Nexus switch. But even if you could have it, it's probably not very useful information to have.