Ethernet Fabric (VDX, CNA)

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Occasional Contributor
Posts: 5
Registered: ‎07-09-2013

Discards on TenGig port

What do Received Discards mean on the ten gig ports? 

Contributor
Posts: 48
Registered: ‎02-27-2012

Re: Discards on TenGig port

[ Edited ]

Hi,

if you have incoming (RX) Discards this means that the buffer for that Queue seems to be full or the threshold for that traffic is reached to the packet is dropped !  -> sh int stats brief

 

We see that often if you have some 10G Servers that communicate with 1G Servers  so there is a massive oversubscribtion and the buffers are not in charge to buffer those peaks. 

 

You should check that discards with Sflow who is gernerating traffic to which destination server and maybe think about a change in the IF Upgrade of the destination to 10G or enable QoS to drop only unimportant traffic - per default all traffic uses the same queue and get dropped if this is exhausted.

 

You can check your drop-port settings with 

sh qos int te 1/0/1

...

Per-Traffic Class Tail Drop Threshold (bytes)
TC: 0 1 2 3 4 5 6 7
------------------------------------------------------------------
Threshold: 252 252 252 75284 252 252 66780 75284

 

Class 3 has 75kb of Threshold - if you don't jhave FCOE you can modify that to 252 and give that Threshold to a differnt class.. 

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