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untagged cos 0

aamercado
Level 4
Level 4

‎05-05-2010 11:23 PM

On N5k design guide, why is "untagged cos 0" recommended on fex facing interface

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Jon Marshall
Hall of Fame
Hall of Fame

‎05-06-2010 05:02 AM 

aamercado wrote:
On N5k design guide, why is "untagged cos 0" recommended on fex facing interface

Good question. The untagged cos command is used to set the CoS value when there is no tag to contain the 802.1p value ie. no vlan tag. The default value for an untagged packet received on an ethernet interface is 0 so you only need to use the "untagged cos .." command when you want to set the CoS value to something other than 0.

So i can't see why you need to specificy it all to be honest. Perhaps some Nexus expert will be able to enlighten both of us

Jon

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Lucien Avramov
Level 10
Level 10
In response to Jon Marshall

‎05-06-2010 09:08 AM

This is because of the way the buffer queues are handled on the FEX.

To allocate maximum buffer and better performance as of now we use cos 0.

Newer code will have improvements.

HTH,

Please support CSC Helps Haiti

https://supportforums.cisco.com/docs/DOC-8895

https://supportforums.cisco.com

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Jon Marshall
Hall of Fame
Hall of Fame
In response to Lucien Avramov

‎05-06-2010 11:37 AM 

lavramov wrote:
This is because of the way the buffer queues are handled on the FEX. 
To allocate maximum buffer and better performance as of now we use cos 0. 
Newer code will have improvements.
HTH,
Please support CSC Helps Haiti
https://supportforums.cisco.com/docs/DOC-8895
  
https://supportforums.cisco.com

Lucien

But if the default is 0 anyway why do you specifically have to configure it.

Jon

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