VSS - lot of giant frames on the VSL

Unanswered Question
Jul 18th, 2008


We have implemented VSS with 2 6509.

We are seeing a lot of giant frames on the VSL. MTU is set to 1500.

I have read in the configuration guide that packets that are sent through the VSL are encapsulated with 32 bytes header.

Is it recommended to change the MTU on the VSL? I didn't see any specific recommendation in the config guide.

Thanks in advance,


I have this problem too.
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a.alekseev Fri, 07/18/2008 - 05:50

There are no recommendations to change the MTU on the VSL.

Stay it as it is.

mduchemin Sun, 07/20/2008 - 23:42

Thanks for your reply.

So I can ignore those giants frames? that would be part of the normal operation of VSS?



Ryan Carretta Mon, 07/21/2008 - 02:23

Giants on the VSL are cosmetic.

Packets get encapsulated in a VSL header when crossing the VSL, and so may be a fair bit larger than 1548 (the size after which a packet gets counted as a giant by the 6k).

The packet size is counted at the media access controller, which has no notion of VSL encapsulation. The encapsulation is later stripped off and the packet is processed.

Normal operation by all counts. :)


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