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Receive Discards on a VLAN...?

Berthold over 13 years ago

NPM is reporting "Receive Discards" on the main VLAN of our main Cisco switch... but none of the network interfaces are reporting this.

What would cause the VLAN to report discards, but none of the network interfaces to do so? We seem to be getting ~100/minute so it's consistent traffic of some type...

0 Berthold over 13 years ago

Anyone? I'm at a loss here...
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0 lchance over 13 years ago

Found this on Cisco, it might get you started...
"A discard can occur because a packet was sent to a TCP/UDP port for which there was no listener. For example, if someone tried to make a telnet connection to the IP address on the VLAN interface, but telnet was disabled."
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0 lchance over 13 years ago

One more thing.
If you can place a sniffer there to catch the traffic. Someone or something could be pounding that IP address with malformed frame sizes to make it get discarded. Good luck!
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0 Berthold over 13 years ago in reply to lchance

Hm. Telnet not disabled; this is the default VLAN. Drops only happening during the day / business hours, so it looks like the cause gets turned off at night.
No way to determine the source of a dropped packet on a core switch? No interfaces are dropping packets, just the VLAN.
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0 nightmare over 13 years ago in reply to Berthold

erm look like you might had CRC error or mismatch duplex setting. did your NPM poll CRC? previously i got this issue with my HP PROCURVE switch..
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0 Donald_Francis over 13 years ago in reply to nightmare

CRC or or duplex mismatches would show as errors not discards.

A vlan interface like any other interface has resources assigned , buffers etc. When these are over run you see discards.
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0 Questionario over 13 years ago in reply to Donald_Francis

if you have access lists on your vlan, the packets that are dropped because of that ACL are shown as discards in orion.
I usually dont even look at discards anymore, only errors
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0 Donald_Francis over 13 years ago in reply to Questionario

I find not looking at discards a scary proposition. They will clue you into an oversubscribed interface before it gets so bad users notice.
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0 Questionario over 13 years ago in reply to Donald_Francis

I agree but you cannot differ the discards on interfaces with ACLs in Orion.
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