storm-control question

Answered Question
Mar 25th, 2010

I'm reviewing some configs that were done before I got here. I had a quick question on storm-control that I've never been sure about. The command "storm-control action trap"... does that just generate traps when passing the threshold levels, or does it filter too? I've seen posts in doing searches that say that it's trap only, and some that say filter and trap. Could it be different for different models and IOSes?

Thanks!

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Correct Answer by johnnylingo about 6 years 8 months ago

Storm Control always does filtering, even if you don't have the "trap".   "trap" will do bother filtering and send SNMP traps.

You can verify the operating using the "show storm-control" command and looking at the interface status. For example:

interface FastEthernet0/1
  storm-control multicast level 50.00
!

Before Storm:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Forwarding     inactive       50.00%   50.00%    0.00%           0

As Storm builds:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Forwarding     inactive       50.00%   50.00%   41.48%           0

After Filtering kicks in:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Blocking       inactive       50.00%   50.00%   75.68%           0

What I'm not sure about is if in "Blocking" state, if it blocks all packets or only a certain percentage.

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Reza Sharifi Thu, 03/25/2010 - 12:58

Hi,

According to the command reference guide this command sends an SNMP trap:

action {shutdown | trap}

Action taken when a storm occurs on a port. The default action is to filter traffic and to not send an Simple Network Management Protocol (SNMP) trap.

The keywords have these meanings:

shutdown—Disables the port during a storm.

trap—Sends an SNMP trap when a storm occurs.

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_25_sea/command/reference/cli3.html#wp2278213

HTH

Reza

spfister336 Thu, 03/25/2010 - 13:14

Yes, that's true, but that's not quite what I was asking. Obviously, using this command a trap is sent when a threshold is passed. What I'm trying to figre out is, one of the following two cases is true:

- a trap is sent and filtering IS done

- a trap is sent and filtering IS NOT done

I've ran across this link and couldn't be certain from what I read.

Correct Answer
johnnylingo Thu, 03/25/2010 - 13:15

Storm Control always does filtering, even if you don't have the "trap".   "trap" will do bother filtering and send SNMP traps.

You can verify the operating using the "show storm-control" command and looking at the interface status. For example:

interface FastEthernet0/1
  storm-control multicast level 50.00
!

Before Storm:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Forwarding     inactive       50.00%   50.00%    0.00%           0

As Storm builds:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Forwarding     inactive       50.00%   50.00%   41.48%           0

After Filtering kicks in:

switch#show storm-control multi
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Blocking       inactive       50.00%   50.00%   75.68%           0

What I'm not sure about is if in "Blocking" state, if it blocks all packets or only a certain percentage.

johnnylingo Thu, 03/25/2010 - 13:22

Here's same situation but with trap:


interface FastEthernet0/1
storm-control multicast level 50.00
storm-control action trap

!


switch#show storm-control multicast
Interface  Filter State   Trap State     Upper    Lower    Current  Traps Sent
---------  -------------  -------------  -------  -------  -------  ----------
Fa0/1      Blocking       Above falling  50.00%   50.00%   75.93%           3

spfister336 Thu, 03/25/2010 - 13:26

OK... that's what I kind of suspected, but I wanted to make sure...

Thanks for the replies!

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