Trouble understanding packet drops

Unanswered Question
Apr 21st, 2008
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I have two 6513 SUP720 connected via a 40km gigabit ethernet trunk using a leased "black fiber" connection.

Recently I've been getting sporadic transmit discard warnings from one of the 6513 in my monitoring software. Doesn't seem to be related to any increase in traffic but suddenly I can see 4000 dropped packets at once. Average packet speed is 38000 packets/sec and no flow control is configured.

Clean/replace GBIC? Increase queues? Flowcontrol?

Any suggestions?


Fredrik Hofgren

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ivillegas Fri, 04/25/2008 - 06:17
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If you are detecting packets drops on the server, then it is

usually an indication that flowcontrol should be enabled. However,

flowcontrol needs to be enabled on both ports. If you cannot enable it

on the nic card of the server, then turn it off on the switch side.

Other than this, you may want to look into possibly using a different

nic card in your server.

The output drops are the number of packets dropped because the output queue is full. A common cause of this might be traffic from a high bandwidth link being switched to a lower bandwidth link or traffic from multiple inbound links being switched to a single outbound link.


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