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clear mac-address-table through flowcontrol
clear mac-address-table
To remove a specified address (or set of addresses) from the MAC address table, use the clearmac-address-tablecommand inprivileged EXEC mode.
Using Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
clear mac-address-table [ dynamic | restricted static | permanent ] [ address mac-address ] [ interface type module port ]
clear mac-address-table notification mac-move counter [vlan]
clear mac-address-table dynamic [ address mac-address | interface interface-type interface-number | vlan vlan-id ]
Syntax Description
Command Default
Using Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
All MAC addresses on the router being configured are cleared.
Using Catalyst Switches
The dynamic addresses are cleared.
Clearing a Dynamic Address
This command has no defaults in this mode.
Command History
Release
Modification
12.2(2)XT
This command was introduced on Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers.
12.2(8)T
This command was integrated into Cisco IOS Release 12.2(8)T on Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers.
12.2(11)T
This command was integrated into Cisco IOS Release 12.2(11)T.
12.2(14)SX
Support for this command was introduced on the Supervisor Engine 720.
12.2(17d)SXB
Support for this command on the Supervisor Engine 2 was extended to Cisco IOS Release 12.2(17d)SXB.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SXI
This command was changed to add the notificationmac-movecounter [vlan] keywords and argument.
Usage Guidelines
Using Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
If the clearmac-address-table command is invoked with no options, all MAC addresses are removed. If you specify an address but do not specify an interface, the address is deleted from all interfaces. If you specify an interface but do not specify an address, all addresses on the specified interface are removed.
Using Catalyst Switches
If the clearmac-address-table command is invoked with no options, all dynamic addresses are removed. If you specify an address but do not specify an interface, the address is deleted from all interfaces. If you specify an interface but do not specify an address, all addresses on the specified interface are removed.
If a targeted address is not present in the MAC forwarding table, the following error message appears:
MAC address not foundClearing a Dynamic Address
The valid values for the interface argument include thege-wan, atm, and pos keywords that are supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2.
The protocol {assigned | ip | ipx| other} keywords are supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2 only.
Enter the clearmac-address-tabledynamic command to remove all dynamic entries from the table.
The following values are valid for interface-type:
Setting the Module and Port
The interface-number argument designates the module and port number. Valid values for interface-number depend on the specified interface type and the chassis and module that are used. For example, if you specify a Gigabit Ethernet interface and have a 48-port 10/100BASE-T Ethernet module that is installed in a 13-slot chassis, valid values for the module number are from 1 to 13 and valid values for the port number are from 1 to 48.
Examples
Using Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
The following example shows how to clear all dynamic addresses in the MAC forwarding table:
Router# clear mac-address-table dynamicThe following example shows how to clear the static address 0040.C80A.2F07 on Ethernet port 1:
Router# clear mac-address-table static address 0040.C80A.2F07 interface ethernet 0/1Using Catalyst Switches
The following example shows how to clear all dynamic addresses in the MAC forwarding table:
Router# clear mac-address-table dynamicThe following example shows how to clear the MAC-move notification counters on a specific VLAN:
Router# clear mac-address-table notification mac-move counter 202The following example shows the permanent address 0040.C80A.2F07 being cleared on Ethernet port 1:
Router# clear mac-address-table permanent address 0040.C80A.2F07 interface ethernet 0/1Clearing a Dynamic Address on a 7600 using a Supervisor Engine 2
This example shows how to clear all dynamic Layer 2 entries for a specific interface (abc) and protocol type (IPX):
Router# clear mac-address-table dynamic interface abc protocol ipxRelated Commands
Command
Description
mac -address-tableaging-time
Configures the length of time the switch keeps dynamic MAC addresses in memory before discarding.
mac -address-tablepermanent
Associates a permanent unicast or multicast MAC address with a particular switched port interface.
mac -address-tablerestrictedstatic
Associates a restricted static address with a particular switched port interface.
mac -address-tablesecure
Associates a secure static address with a particular switched port interface.
mac-address-table static
Adds static entries to the MAC-address table or configures a static MAC address with IGMP snooping disabled for that address.
show mac -address-table
Displays addresses in the MAC address table for a switched port or module.
show mac -address-tablesecure
Displays the addressing security configuration.
show mac -address-tablesecurity
Displays the addressing security configuration.
clear pagp
clear vtp counters
To clear VLAN Trunk Protocol (VTP) counters, use the clearvtpcounters command in privileged EXEC mode.
Command History
Release
Modification
15.0(1)M
This command was introduced in a release earlier than Cisco IOS Release 15.0(1)M.
12.2(33)SRE
This command was integrated into a release earlier than Cisco IOS Release 12.2(33)SRE.
12.2(33)SXI
This command was integrated into a release earlier than Cisco IOS Release 12.2(33)SXI.
flowcontrol
To configure a port to send or receive pause frames, use the flowcontrol command in interface configuration mode. To return to the default settings, use the no form of this command.
flowcontrol { send | receive } { desired | off | on }
no flowcontrol { send | receive } { desired | off | on }
Syntax Description
send
Specifies that a port sends pause frames.
receive
Specifies that a port processes pause frames.
desired
Obtains predictable results regardless of whether a remote port is set to on, off, or desired.
off
Prevents a local port from receiving and processing pause frames from remote ports or from sending pause frames to remote ports.
on
Enables a local port to receive and process pause frames from remote ports or send pause frames to remote ports.
Command Default
Flow control is disabled.
Flow-control defaults depend upon port speed. The defaults are as follows:
- Gigabit Ethernet ports default to off for receive and desired for send.
- Fast Ethernet ports default to off for receive and on for send.
- On the 24-port 100BASE-FX and 48-port 10/100 BASE-TX RJ-45 modules, the default is off for receive and off for send.
- You cannot configure how WS-X6502-10GE 10-Gigabit Ethernet ports respond to pause frames. WS-X6502-10GE 10-Gigabit Ethernet ports are permanently configured to respond to pause frames.
Command History
Release
Modification
12.2(14)SX
This command was introduced on the Supervisor Engine 720.
12.2(17d)SXB
This command was implemented on the Supervisor Engine 2.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
12.2(33)SCB
This command was integrated into Cisco IOS Release 12.2(33)SCB.
Usage Guidelines
The send and desired keywords are supported on Gigabit Ethernet ports only.
Pause frames are special packets that signal a source to stop sending frames for a specific period of time because the buffers are full.
Gigabit Ethernet ports on the Catalyst 6500 series switches and on the Cisco 7600 series routers use flow control to inhibit the transmission of packets to the port for a period of time; other Ethernet ports use flow control to respond to flow-control requests.
If a Gigabit Ethernet port receive buffer becomes full, the port transmits a “pause” packet that tells remote ports to delay sending more packets for a specified period of time. All Ethernet ports (1000 Mbps, 100 Mbps, and 10 Mbps) can receive and act upon “pause” packets from other devices.
You can configure non-Gigabit Ethernet ports to ignore received pause frames (disable) or to react to them (enable).
When used with the receivekeyword, the on and desired keywords have the same result.
All the Gigabit Ethernet ports on the Catalyst 6500 series switches and the Cisco 7600 series routers can receive and process pause frames from remote devices.
To obtain predictable results, follow these guidelines:
- Use sendon only when remote ports are set to receiveon or receivedesired.
- Use sendoff only when remote ports are set to receiveoff or receivedesired.
- Use receiveon only when remote ports are set to sendon or senddesired.
- Use sendoff only when remote ports are set to receiveoff or receivedesired.
Examples
These examples show how to configure the local port to not support any level of flow control by the remote port:
Router# configure terminal Router(config)# interface GigabitEthernet1/9 10.4.9.157 255.255.255.0 Router(config-if)# flowcontrol receive off Router(config-if)# flowcontrol send off