I had a customer call in the other day asking about NetFlow with VSS. I had no idea so I decided to learn about ‘VSS’. I made call to my CCIE friend Chuck Cahoon at CDW.

Chuck CahoonSolutions Architect – CDW
Cisco Systems CCIE# 15255
E-mail: [email protected]
Chuck explained “Some reasons to use Cisco VSS are to get rid of spanning-tree between the distribution and access layers.

“Today’s access switch connecting to your distribution using spanning-tree would usually be dual-homed, meaning connecting to two separate distribution switches. With spanning-tree, in most cases, one of the uplinks will be unused for a given VLAN. The second uplink is unused and only for redundancy (you can balance VLANs to even things out, but that has to be configured).

“With VSS your access switch would have only one port channel that would actually connect to both distribution switches. From the perspective of the access switch, it’s only connecting to a single switch (even though it’s physically two separate switches). Since we only have one port-channel to the distribution, HSRP or VRRP is not needed. One VLAN IP is assigned to the VSS distribution switch, and clients use that as default gateway. Load balancing across links is done using the traditional etherchannel hashing algorithm. VSS is used on the 6500 chassis. If you have the new VS-S720-10G-3C supervisor it is worth looking into this technology.”

If you have questions on this, call Chuck, not me! I read online that VSS also offers a 20 fold improvement in failover times. Anyway, I asked and of course NetFlow should work fine. Thanks Chuck!

Joanne Ghidoni author pic

Joanne Ghidoni

Joanne is a Software Quality Assurance Engineer at Plixer. She has also held positions as Technical Support Engineer and Sales Engineer since joining Plixer in 2005. Prior to joining Plixer, Joanne has had numerous positions in the IT field, including data entry, computer operator, PC coordinator and support, mainframe programmer, and also Technical Support and web programmer at Cabletron Systems. In her spare time, Joanne enjoys traveling, always seeking out new and interesting places to visit.


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