Extreme X460 with high CPU and packets going to CPU

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Hello Guys, 

I'm living a problem in our MPLS network and would like to share you experience.
One of our Extreme X460 switch is experiencing high CPU load and with process mpls and bcmRX in the top of the processes with high utilisation.

using show l2stats we saw that between our many vlans, three (3) of them are sending abnormal amount of packets to CPU. 

In the begging we have tried to capture the traffic of this vlans, but there is a huge amount of traffic, and I wasn't able to determine with packets are been really sent to cpu.

So, I would like your help is this two topics:  

1. How can i determine exactly with packets in that VLAN are being sent to CPU ? Is there any sniffer, debug of monitor inside EXOS that I can have a sample of this packets ? 

2. How can I prevent packets from being sent to CPU.  Considering that one of this vlans are just an L2 vlans between two ports, and we don't have L3 IP address on the vlan, I was not suppose to receive any packets on CPU except by protocols packets... How can I create filters for that  ? Any sugestions ?

Thanks a lot for any help.

Epafras Schaden
Network Engineering - Durand Tavola
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Epafras Schaden

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Posted 3 months ago

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Paolo Trivisonno

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I’ve got an problem like this.. have you check if some acl applied to this vlan use mirror-cpu?
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Epafras Schaden

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Hello Paolo... Checked, but I don't have any ACL or mirror configured on this switch...
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EtherMAN, Embassador

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the trick here is understanding what type of packets the cpu processes.... I know a few.. Broacast traffic, unknown mac address, mcast joins and prunes.. 

Quick search i found this post that will get you started https://extremeportal.force.com/ExtrArticleDetail?n=000015071&q=packets%20that%20go%20to%20cpu%2... 

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Necheporenko, Nikolay, Employee

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Hello Epafras,

>>> 1. How can i determine exactly...

x670v-48x[29].169 # debug packet capture on interface Broadcom count 15000

x670v-48x[29].170 # ls /usr/local/tmp
-rwxr-xr-x    1 root     root         2616 Feb 13 14:07 2015-02-13_14-07-09_rx_tx.pcap
-rwxr-xr-x    1 root     root          217 Feb 13 14:07 capture.log 
1K-blocks      Used Available Use%
    118160       230    117930   0%
x670v-48x[29].171 # tftp put /usr/local/tmp/2015-02-13_14-07-09_rx_tx.pcap /2015-02-13_14-07-09_rx_tx.pcap
Uploading 2015-02-13_14-07-09_rx_tx.pcap to ... done!
>>> 2. How can I prevent packets from being sent to CPU...
This is could be already known issue which is fixed in the latest EXOS. Please check Release Notes.
As workaround before upgrade, you may try to run command <restart process mpls>.