Configuring Storm Control

This chapter describes how to configure port-based traffic control on the Catalyst 4500 series switch.

This chapter consists of these sections:

•About Storm Control

•Enabling Broadcast Storm Control

•Enabling Multicast Storm Control

•Disabling Broadcast Storm Control

•Disabling Multicast Storm Control

•Displaying Storm Control

Note For complete syntax and usage information for the switch commands used in this chapter, look at the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/hw/switches/ps4324/index.html

If the command is not found in the Catalyst 4500 Command Reference, it is located in the larger Cisco IOS library. Refer to the Catalyst 4500 Series Switch Cisco IOS Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/ps6350/index.html

About Storm Control

This section contains the following subsections:

•Hardware-based Storm Control Implementation

•Software-based Storm Control Implementation

Storm control prevents LAN interfaces from being disrupted by a broadcast storm. A broadcast storm occurs when broadcast packets flood the subnet, creating excessive traffic and degrading network performance. Errors in the protocol-stack implementation or in the network configuration can cause a broadcast storm.

Note Storm control and Multicast storm control are supported in hardware on all ports on Supervisor Engine 7-E.

Hardware-based Storm Control Implementation

Broadcast suppression uses filtering that measures broadcast activity in a subnet over a one-second interval and compares the measurement with a predefined threshold. If the threshold is reached, further broadcast activity is suppressed for the duration of the interval. Broadcast suppression is disabled by default.

Figure 45-1 shows the broadcast traffic patterns on a LAN interface over a given interval. In this example, broadcast suppression occurs between times T1 and T2 and between T4 and T5. During those intervals, the amount of broadcast traffic exceeded the configured threshold.

Figure 45-1 Storm Control Example - Hardware-based Implementation

The broadcast suppression threshold numbers and the time interval combination make the broadcast suppression algorithm work with different levels of granularity. A higher threshold allows more broadcast packets to pass through.

Broadcast suppression on the Catalyst 4500 series switches (including Supervisor Engine 7-E) is implemented in hardware. The suppression circuitry monitors packets passing from a LAN interface to the switching bus. If the packet destination address is broadcast, then the broadcast suppression circuitry tracks the current count of broadcasts within the one-second interval, and when a threshold is reached, it filters out subsequent broadcast packets.

Because hardware broadcast suppression uses a bandwidth-based method to measure broadcast activity, the most significant implementation factor is setting the percentage of total available bandwidth that can be used by broadcast traffic. Because packets do not arrive at uniform intervals, the one-second interval during which broadcast activity is measured can affect the behavior of broadcast suppression.

Software-based Storm Control Implementation

When storm control is enabled on an interface, the switch monitors packets received on the interface and determines whether the packets are broadcast. The switch monitors the number of broadcast packets received within a one-second time interval. When the interface threshold is met, all incoming data traffic on the interface is dropped. This threshold is specified as a percentage of total available bandwidth that can be used by broadcast traffic. If the lower threshold is specified, all data traffic is forwarded as soon as the incoming traffic falls below that threshold.

Enabling Broadcast Storm Control

To enable storm control, perform this task:

 
Command
Purpose

Step 1  

Switch# configure terminal

Enters global configuration mode.

Step 2  

Switch(config)# interface interface-id

Enters interface configuration mode and enter the port to configure.

Step 3  

Switch(config-if)# storm-control 
broadcast level [high level] [lower 
level]

Configures broadcast storm control.

Specifies the upper threshold levels for broadcast traffic. The storm control action occurs when traffic utilization reaches this level.

(Optional) Specifies the falling threshold level. The normal transmission restarts (if the action is filtering) when traffic drops below this level for interfaces that support software-based suppression.

Note For ports that perform hardware-based suppression, the lower threshold is ignored.

Step 4  

Switch(config-if)# storm-control action 
{shutdown | trap}

Specifies the action to be taken when a storm is detected.

The default is to filter out the broadcast traffic and not to send out traps.

The shutdown keyword sets the port to error-disable state during a storm. If the recover interval is not set, the port remains in shutdown state.

Step 5  

Switch(config-if)# exit

Returns to configuration mode.

Step 6  

Switch(config)# end

Returns to privileged EXEC mode.

Step 7  

Switch# show storm-control [interface] 
broadcast

Displays the number of packets suppressed.

Step 8  

Switch# copy running-config 
startup-config

(Optional) Saves your entries in the configuration file.

The following example shows how to enable storm control on interface. 

Switch# configure terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Switch(config)# interface fa3/1

Switch(config-if)# storm-control broadcast level 50

Switch(config-if)# end

 
   
 
    
   
 
    
Switch# show storm-control 

 
   
 
    
   
 
    
Interface  Filter State   Broadcast Multicast Level

 
   
 
    
   
 
    
---------  -------------  --------- --------- -----

 
   
 
    
   
 
    
Fi3/1      Forwarding     Enabled   Disabled  50.00% 

 
   
 
    
   
 
    
 
   
 
    
   
 
    
Switch# show int fa2/1 capabilities 

 
   
 
    
   
 
    
FastEthernet2/1

 
   
 
    
   
 
    
  Model:                 WS-X4148-RJ45V-RJ-45

 
   
 
    
   
 
    
  Type:                  10/100BaseTX

 
   
 
    
   
 
    
  Speed:                 10,100,auto

 
   
 
    
   
 
    
  Duplex:                half,full,auto

 
   
 
    
   
 
    
  Auto-MDIX:             no

 
   
 
    
   
 
    
  Trunk encap. type:     802.1Q

 
   
 
    
   
 
    
  Trunk mode:            on,off,desirable,nonegotiate

 
   
 
    
   
 
    
  Channel:               yes

 
   
 
    
   
 
    
  Broadcast suppression: percentage(0-100), hw

 
   
 
    
   
 
    
  Multicast suppression: percentage(0-100), hw 

 
   
 
    
   
 
    
  Flowcontrol:           rx-(none),tx-(none)

 
   
 
    
   
 
    
  VLAN Membership:       static, dynamic

 
   
 
    
   
 
    
  Fast Start:            yes

 
   
 
    
   
 
    
  CoS rewrite:           yes

 
   
 
    
   
 
    
  ToS rewrite:           yes

 
   
 
    
   
 
    
  Inline power:          yes (Cisco Voice Protocol)

 
   
 
    
   
 
    
  SPAN:                  source/destination

 
   
 
    
   
 
    
  UDLD:                  yes

 
   
 
    
   
 
    
  Link Debounce:         no

 
   
 
    
   
 
    
  Link Debounce Time:    no

 
   
 
    
   
 
    
  Port Security:         yes

 
   
 
    
   
 
    
  Dot1x:                 yes

 
   
 
    
   
 
    
  Maximum MTU:           1552 bytes (Baby Giants)

 
   
 
    
   
 
    
  Multiple Media Types:  no

 
   
 
    
   
 
    
  Diagnostic Monitoring: N/A\

 
   
 
    
   
 
    
 
   
 
   
 
     
   
 
   
 
    
   
 Note Supervisor Engine 7-E supports multicast suppression 
 
   
 
     
    
    
    
   
 Enabling Multicast Storm Control 
 
    
    
   
 Supervisor Engine 7-E supports per-interface multicast suppression. 
 
    
   
 This allows the user to subject incoming multicast and broadcast traffic on an interface to suppression. 
 
   
 
     
   
 
   
 
    
   
 Note Multicast and broadcast suppression share a common threshold per interface.
Multicast suppression takes effect only if broadcast suppression is enabled.
Disabling broadcast suppression on an interface also disables multicast suppression. 
 
   
 
    
   
 To enable multicast suppression, perform this task: 
 
    
   
 
 
   
 
    
 
      
      
      
 
         
        
        

          Command 
        
 		 
        
        

          Purpose 
        
 		 
      
 
      
 
       
 Step 1  
 		 
        
        
 
         
Switch# configure terminal

 
        
 
       
 Enters global configuration mode. 
 		 
      
 
      
 
       
 Step 2  
 		 
        
        
 
         
Switch(config)# interface interface-id

 
        
 
       
 Enters interface configuration mode and enter the port to configure. 
 		 
      
 
      
 
       
 Step 3  
 		 
        
        
 
         
Switch(config-if)# storm-control 
broadcast include multicast

 
        
 
       
 Enables multicast suppression. 
 		 
      
 
      
 
       
 Step 4  
 		 
        
        
 
         
Switch(config-if)# exit

 
        
 
       
 Returns to configuration mode. 
 		 
      
 
      
 
       
 Step 5  
 		 
        
        
 
         
Switch(config)# end

 
        
 
       
 Returns to privileged EXEC mode. 
 		 
      
 
      
 
       
 Step 6  
 		 
        
        
 
         
Switch# show storm-control

 
        
 
       
 Verifies the configuration. 
 		 
      
 
      
    
 
   
 
   
 
 
    
   
 The following example shows how to enable multicast suppression on ports that have broadcast suppression already enabled: 
 
    
   
 
    
Switch# configure terminal

 
   
 
    
   
 
    
Enter configuration commands, one per line.  End with CNTL/Z.

 
   
 
    
   
 
    
Switch(config)# int fa3/1

 
   
 
    
   
 
    
Switch(config-if)# storm-control broadcast include multicast

 
   
 
    
   
 
    
Switch(config-if)# end

 
   
 
    
   
 
    
Switch#

 
   
 
    
   
 
    
Switch# show storm-control

 
   
 
    
   
 
    
Interface  Filter State   Broadcast Multicast Level

 
   
 
    
   
 
    
---------  -------------  --------- --------- -----

 
   
 
    
   
 
    
Fi3/1      Forwarding     Enabled   Enabled   50.00%

 
   
 
     
    
    
    
    
    
   
 Disabling Broadcast Storm Control 
 
    
   
 To disable storm control, perform this task: 
 
    
   
 
 
   
 
    
 
      
      
      
 
         
        
        

          Command 
        
 		 
        
        

          Purpose 
        
 		 
      
 
      
 
       
 Step 1  
 		 
        
        
 
         
Switch# configure terminal

 
        
 
       
 Enters global configuration mode. 
 		 
      
 
      
 
       
 Step 2  
 		 
        
        
 
         
Switch(config)# interface interface-id

 
        
 
       
 Enters interface configuration mode and enter the port to configure. 
 		 
      
 
      
 
       
 Step 3  
 		 
        
        
 
         
Switch(config-if)# no storm-control 
broadcast level 

 
        
 
       
 Disables port storm control. 
 		 
      
 
      
 
       
 Step 4  
 		 
        
        
 
         
Switch(config-if)# no storm-control action 
{shutdown | trap}

 
        
 
       
 Disables the specified storm control action and returns to default filter action. 
 		 
      
 
      
 
       
 Step 5  
 		 
        
        
 
         
Switch(config-if)# exit

 
        
 
       
 Returns to configuration mode. 
 		 
      
 
      
 
       
 Step 6  
 		 
        
        
 
         
Switch(config)# end

 
        
 
       
 Returns to privileged EXEC mode. 
 		 
      
 
      
 
       
 Step 7  
 		 
        
        
 
         
Switch# show storm-control broadcast 

 
        
 
       
 Verifies your entries. 
 		 
      
 
      
 
       
 Step 8  
 		 
        
        
 
         
Switch# copy running-config startup-config

 
        
 
       
 (Optional) Saves your entries in the configuration file. 
 		 
      
 
      
    
 
   
 
   
 
 
    
   
 The following example shows how to disable storm control on interface. 
 
    
   
 
    
Switch# configure terminal

 
   
 
    
   
 
    
Enter configuration commands, one per line.  End with CNTL/Z.

 
   
 
    
   
 
    
Switch(config)# int fa3/1

 
   
 
    
   
 
    
Switch(config-if)# no storm-control broadcast level 

 
   
 
    
   
 
    
Switch(config-if)# end

 
   
 
    
   
 
    
Switch# show storm-control 

 
   
 
    
   
 
    
Interface  Filter State   Upper    Lower    Current

 
   
 
    
   
 
    
---------  -------------  -------  -------  -------

 
   
 
    
   
 
    
Switch#

 
   
 
     
    
    
    
   
 Disabling Multicast Storm Control 
 
    
   
 To disable multicast suppression, perform this task: 
 
    
   
 
 
   
 
    
 
      
      
      
 
         
        
        

          Command 
        
 		 
        
        

          Purpose 
        
 		 
      
 
      
 
       
 Step 1  
 		 
        
        
 
         
Switch# configure terminal

 
        
 
       
 Enters global configuration mode. 
 		 
      
 
      
 
       
 Step 2  
 		 
        
        
 
         
Switch(config)# [no] storm-control 
broadcast include multicast

 
        
 
       
 Enables/disables multicast suppression. 
 		 
      
 
      
 
       
 Step 3  
 		 
        
        
 
         
Switch(config-if)# no storm-control 
broadcast level

 
        
 
       
 Disables port storm control (broadcast and multicast). 
 		 
      
 
      
 
       
 Step 4  
 		 
        
        
 
         
Switch(config-if)# end

 
        
 
       
 Returns to configuration mode. 
 		 
      
 
      
 
       
 Step 5  
 		 
        
        
 
         
Switch(config)# end

 
        
 
       
 Returns to privileged EXEC mode. 
 		 
      
 
      
    
 
   
 
   
 
 
     
    
    
    
   
 Displaying Storm Control 
 
   
 
     
   
 
   
 
    
   
 Note Use the show interface capabilities command to determine the mode in which storm control is supported on an interface. 
 
   
 
    
   
 The following example shows an interface that supports broadcast suppression in software (sw). 
 
    
   
 
    
Switch# show int fa2/1 capabilities

 
   
 
    
   
 
    
FastEthernet2/1

 
   
 
    
   
 
    
  Model:                 WS-X4148-RJ45V-RJ-45

 
   
 
    
   
 
    
  Type:                  10/100BaseTX

 
   
 
    
   
 
    
  Speed:                 10,100,auto

 
   
 
    
   
 
    
  Duplex:                half,full,auto

 
   
 
    
   
 
    
  Auto-MDIX:             no

 
   
 
    
   
 
    
  Trunk encap. type:     802.1Q

 
   
 
    
   
 
    
  Trunk mode:            on,off,desirable,nonegotiate

 
   
 
    
   
 
    
  Channel:               yes

 
   
 
    
   
 
    
  Broadcast suppression: percentage(0-100), hw

 
   
 
    
   
 
    
  Multicast suppression: percentage(0-100), hw 

 
   
 
    
   
 
    
  Flowcontrol:           rx-(none),tx-(none)

 
   
 
    
   
 
    
  VLAN Membership:       static, dynamic

 
   
 
    
   
 
    
  Fast Start:            yes

 
   
 
    
   
 
    
  CoS rewrite:           yes

 
   
 
    
   
 
    
  ToS rewrite:           yes

 
   
 
    
   
 
    
  Inline power:          yes (Cisco Voice Protocol)

 
   
 
    
   
 
    
  SPAN:                  source/destination

 
   
 
    
   
 
    
  UDLD:                  yes

 
   
 
    
   
 
    
  Link Debounce:         no

 
   
 
    
   
 
    
  Link Debounce Time:    no

 
   
 
    
   
 
    
  Port Security:         yes

 
   
 
    
   
 
    
  Dot1x:                 yes

 
   
 
    
   
 
    
  Maximum MTU:           1552 bytes (Baby Giants)

 
   
 
    
   
 
    
  Multiple Media Types:  no

 
   
 
    
   
 
    
  Diagnostic Monitoring: N/A

 
   
 
   
 
     
   
 
   
 
    
   
 Note Use the show interfaces counters storm-control command to display a count of discarded packets. 
 
   
 
    
   
 
    
Switch# show interfaces counters storm-control

 
   
 
    
   
 
    
Port         Broadcast   Multicast           Level    TotalSuppressedPackets

 
   
 
    
   
 
    
Fa2/1          Enabled    Disabled          10.00%              46516510

 
   
 
    
   
 
    
Gi3/1          Enabled     Enabled          50.00%                     0

 
   
 
    
   
 
    
 
   
 
    
   
 The following example shows the output of the show storm-control command: 
 
    
   
 
    
Switch# show storm-control 

 
   
 
    
   
 
    
Interface  Filter State   Upper    Lower    Current

 
   
 
    
   
 
    
---------  -------------  -------  -------  -------

 
   
 
    
   
 
    
Gi4/4      Forwarding       2.00%    2.00%    N/A

 
   
 
    
   
 
    
Switch

 
   
 
   
 
     
   
 
   
 
    
   
 Note In the previous example, "current" represents the percentage of traffic suppressed at a given instant, and the value is N/A for ports that perform suppression in hardware. 
 
   
 
    
   
 
    
Switch# show storm-control 

 
   
 
    
   
 
    
Interface  Filter State   Broadcast Multicast Level

 
   
 
    
   
 
    
---------  -------------  --------- --------- -----

 
   
 
    
   
 
    
Fa2/1      Blocking       Enabled   Disabled   10.00%   

 
   
 
    
   
 
    
Gi3/1      Link Down      Enabled   Enabled    50.00%