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?