Table Of Contents
channel-group (Fast EtherChannel)
Interface Commands
This chapter describes the basic commands that can be used on different types of interfaces. These commands correspond to the interface configuration tasks included in the Cisco IOS configuration guides. Refer to the configuration guide indicated here for configuration guidelines:
Other interface commands, specific to a particular technology area, are described in the technology specific configuration guides. For hardware technical descriptions, and for information about installing the router or access server interfaces, refer to the hardware installation and maintenance publication for your particular product.
access-list (standard)
Use the access-list global configuration command to establish MAC address access lists. Use the no form of this command to remove a single access list entry.
access-list access-list-number {permit | deny} address mask
no access-list access-list-numberSyntax Description
Default
No MAC address access lists are established.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Related Commands
access-list (type-code)
access-list (type-code)
Use the access-list global configuration command to build type-code access lists. Use the no form of this command to remove a single access list entry.
access-list access-list-number {permit | deny} type-code wild-mask
no access-list access-list-numberSyntax Description
Default
No type-code access lists are built.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Type-code access lists can have an impact on system performance; therefore, keep the lists as short as possible and use wildcard bit masks whenever possible.
Access lists are evaluated according to the following algorithm:
•
If the packet is Ethernet Type II or SNAP, the type-code field is used.
•
If the length/type field is greater than 1500, the packet is treated as an LSAP packet unless the DSAP and SSAP fields are AAAA. If the latter is true, the packet is treated using type-code filtering.
If you have both Ethernet Type II and LSAP packets on your network, you should set up access lists for both.
Use the last item of an access list to specify a default action; for example, permit everything else or deny everything else. If nothing else in the access list matches, the default action is normally to deny access; that is, filter out all other type codes.
Related Commands
access-list (extended)
access-list (standard)aps authenticate
To enable authentication and specify the string that must be present to accept any packet on the out-of-band (OOB) communications channel on a packet-over-SONET (POS) interface, use the aps authenticate interface configuration command. Use the no form of this command, to disable authentication.
aps authenticate string
no aps authenticateSyntax Description
string
Text that must be present to accept the packet on a protected or working interface. Up to eight alphanumeric characters are accepted.
Default
Authentication is disabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps authenticate command to ensure that only valid packets are accepted on the OOB communication channel.
The aps authenticate command must be configured on both the working and protect interfaces.
Example
The following example enables authentication on POS interface 0 in slot 4:
router# configure terminalrouter(config)# interface pos 4/0/0router(config-if)# aps working 1router(config-if)# aps authenticate sanjoserouter(config-if)# exitrouter(config)# exitrouter#Related Commands
aps force
To manually switch the specified circuit to a protect interface, unless a request of equal or higher priority is in effect, use the aps force interface configuration command. Use the no form of this command, to cancel the switch.
aps force circuit-number
no aps force circuit-numberSyntax Description
Default
No circuit is switched.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps force command to manually switch the interface to a protect interface when you are not using the aps revert command. For example, if you need to change the fiber connection, you can manually force the working interface to switch to the protect interface.
In a one-plus-one (1+1) configuration only, you can use the aps force 0 command to force traffic from the protect interface back onto the working interface.
The aps force command has a higher priority than any of the signal failures or the aps manual command.
The aps force command is configured only on protect interfaces.
Example
The following example forces the circuit on POS interface 0 in slot 3 (a protect interface) back onto a working interface:
router# configure terminalrouter(config)# interface pos 3/0/0router(config-if)# aps protect 1router(config-if)# aps force 1router(config-if)# exitrouter(config)# exitrouter#Related Commands
aps manual
aps protect
aps workingaps group
To allow more than one protect and working interface to be supported on a router, use the aps group interface configuration command. Use the no form of this command, to remove a group.
aps group group-number
no aps group group-numberSyntax Description
Default
No groups exist.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps group command to specify more than one working and protect interfaces on a router. For example, working channel for group 0 and protect channel for group 1 on one router, and working channel for group 1 and protect channel for group 0 on another router.
The aps group command must be configured on both the protect and working interfaces.
Example
The following example configures two working/protect interface pairs. Working interface (3/0/0) is configured in group 10 (the protect interface for this working interface is configured on another router), and protect interface (2/0/1) is configured in group 20:
router# configure terminalrouter(config)# interface ethernet 0/0router(config-if)# ip address 7.7.7.6 255.255.255.0router(config)# interface pos 3/0/0router(config-if)# aps group 10router(config-if)# aps working 1router(config)# interface pos 2/0/1router(config-if)# aps group 20router(config-if)# aps protect 1 7.7.7.7router(config-if)# endOn the second router, protect interface (4/0/0) is configured in group 10, and working interface (5/0/0) is configured in group 20 (the protect interface for this working interface is configured on another router):
router(config)# interface ethernet 0/0router(config-if)# ip address 7.7.7.7 255.255.255.0router(config)# interface pos 4/0/0router(config-if)# aps group 10router(config-if)# aps protect 1 7.7.7.6router(config)# interface pos 5/0/0router(config-if)# aps group 20router(config-if)# aps working 1router(config)# endrouter#Related Commands
aps lockout
To prevent a working interface from switching to a protect interface, use the aps lockout interface configuration command. Use the no form of this command, to remove the lockout.
aps lockout circuit-number
no aps lockout circuit-numberSyntax Description
Default
No lockout exists.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
The aps lockout command is configured only on protect interfaces.
Example
The following example locks out (that is, prevents the circuit from switching to a protect interface in the event that the working circuit becomes unavailable) the POS interface 3/0/0:
router# configure terminalrouter(config)# interface pos 3/0/0router(config-if)# aps protect 1 7.7.7.7router(config-if)# aps lockout 1router(config-if)# endrouter#Related Commands
aps manual
To manually switch a circuit to a protect interface, use the aps manual interface configuration command. Use the no form of this command, to cancel the switch.
aps manual circuit-number
no aps manual circuit-numberSyntax Description
Default
No circuit is switched.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps manual command to manually switch the interface to a protect interface. For example, you can use this feature when you need to perform maintenance on the working channel. If a protection switch is already up, you can also use the aps manual command to revert the communication link back to the working interface before the wait to restore (WTR) time has expired. The WTR time period is set by the aps revert command.
In a one-plus-one (1+1) configuration only, you can use the aps manual 0 command to force traffic from the protect interface back onto the working interface.
The aps manual command is a lower priority than any of the signal failures or the aps force command.
Example
The following example forces the circuit on POS interface 0 in slot 3 (a working interface) back onto the protect interface:
router# configure terminalrouter(config)# interface pos 3/0/0router(config-if)# aps working 1router(config-if)# aps manual 1router(config-if)# endrouter#Related Commands
aps force
aps protect
aps revert
aps workingaps protect
To enable a POS interface as a protect interface, use the aps protect interface command. Use the no form of this command, to remove the POS interface as a protect interface.
aps protect circuit-number ip-address
no aps protect circuit-number ip-addressSyntax Description
circuit-number
Number of the circuit to enable as a protect interface.
ip-address
IP address of the router that has the working POS interface.
Default
No circuit is protected.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps protect command to configure the POS interface used by a working interface if the working interface becomes unavailable due to a router failure, degradation or loss of channel signal, or manual intervention.
Note
Example
The following example configures circuit 1 on POS interface 5/0/0 as a protect interface for the working interface on the router with the IP address of 7.7.7.7. For information on how to configure the working interface, refer to the aps working command.
router# configure terminalrouter(config)# interface pos 5/0/0router(config-if)# aps protect 1 7.7.7.7router(config-if)# endrouter#Related Commands
aps revert
To enable automatic switchover from the protect interface to the working interface after the working interface becomes available, use the asp revert interface command. Use the no form of this command, to disable automatic switchover.
aps revert minutes
no aps revertSyntax Description
minutes
Number of minutes until the circuit is switched back to the working interface after the working interface is available.
Default
Automatic switchover is disabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps revert command to return the circuit to the working interface when it becomes available.
The asp revert command is configured only on protect interfaces.
Example
The following example enables circuit 1 on POS interface 5/0/0 to revert to the working interface after the working interface has been available for 3 minutes:
router# configure terminalrouter(config)# interface pos 5/0/0router(config-if)# aps protect 1 7.7.7.7router(config-if)# aps revert 3router(config-if)# endrouter#Related Commands
aps timers
To change the time between hello packets and the time before the protect interface process declares a working interface's router to be down, use the aps timers interface configuration command. Use the no form of this command, to return to the default timers.
aps timers seconds1 seconds2
no aps timersSyntax Description
Default
Hello time is 1 second, and hold time is 3 seconds.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps timers command to control the time between an automatic switchover from the protect interface to the working interface after the working interface becomes available.
Normally, the hold time is greater than or equal to three times the hello time.
The aps timers command is configured only on protect interfaces.
Example
The following example specifies a hello time of 2 seconds and a hold time of 6 seconds on circuit 1 on POS interface 5/0/0:
router# configure terminalrouter(config)# interface pos 5/0/0router(config-if)# aps working 1router(config-if)# aps timers 2 6router(config-if)# endrouter#aps unidirectional
To configure a protect interface for unidirectional mode, use the aps unidirectional interface configuration command. Use the no form of this command, to return to the default, bidirectional mode.
aps unidirectional
no aps unidirectionalSyntax Description
This command has no arguments or keywords.
Default
Bidirectional mode.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
Use the aps unidirectional command when you must interoperate with SONET network equipment (ADMs) that supports unidirectional mode.
Note
The asp unidirectional command is configured only on protect interfaces.
Example
The following example configures POS interface 3/0/0 for unidirectional mode:
router# configure terminalrouter(config)# interface pos 3/0/0router(config-if)# aps unidirectionalrouter(config-if)# aps protect 1 7.7.7.7router(config-if)# endrouter#aps working
To configure a POS interface as a working interface, use the aps working interface configuration command. Use the no form of this command, to remove the protect from the POS interface.
aps working circuit-number
no aps working circuit-numberSyntax Description
Default
No circuit is configured as working.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
When a working interface becomes unavailable because of a router failure, degradation or loss of channel signal, or manual intervention, the circuit is switched to the protect interface to maintain the connection.
To enable the circuit on the protect interface to switch back to the working interface after the working interface becomes available again, use the aps revert interface configuration command.
Note
Example
The following example configures the POS interface 0 in slot 4 as a working interface. For information on how to configure the protect interface, refer to the aps protect command.
router# configure terminalrouter(config)# interface pos 4/0/0router(config-if)# aps working 1router(config-if)# endrouter#Related Commands
atm sonet
To set the mode of operation and thus control the type of the ATM cell used for cell-rate decoupling on the SONET PLIM, use the atm sonet interface configuration command. Use the no form of this command, to restore the default Synchronous Transport Signal level 12, concatenated (STS-12c) operation.
atm sonet [stm-4]
no atm sonet [stm-4]Syntax Description
stm-4
(Optional) Synchronous Digital Hierarchy/Synchronous Transport Signal level 4 (SDH/STM-4) operation (ITU-T specification).
Default
STS-12c
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CC.
This command was modified in Cisco IOS Release 11.2 GS to add the stm-4 keyword.
Use STM-4 in applications where SDH framing is required.
Use the default (STS-12c) in applications where the ATM switch requires "unassigned cells" for rate adaptation. An unassigned cell contains 32 zeros.
Example
The following example sets the mode of operation to SONET STM-4 on ATM interface 3/0:
Router(config)#interface atm 3/0Router(config-if)#atm sonet stm-4Router(config-if)#endRouter#auto-polarity
To enable automatic receiver polarity reversal on a hub port connected to an Ethernet interface of a Cisco 2505 or Cisco 2507, use the auto-polarity hub configuration command. Use the no form of this command, to disable this feature.
auto-polarity
no auto-polaritySyntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Hub configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
This command applies to a port on an Ethernet hub only.
Example
The following example enables automatic receiver polarity reversal on hub 0, ports 1 through 3:
hub ethernet 0 1 3auto-polarityRelated Commands
hub
bandwidth
To set a bandwidth value for an interface, use the bandwidth interface configuration command. Use the no form of this command to restore the default values.
bandwidth kilobits
no bandwidthSyntax Description
kilobits
Intended bandwidth in kilobits per second. For a full bandwidth DS3, enter the value 44736.
Default
Default bandwidth values are set during startup and can be displayed with the EXEC command show interfaces.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The bandwidth command sets an informational parameter only; you cannot adjust the actual bandwidth of an interface with this command. For some media, such as Ethernet, the bandwidth is fixed; for other media, such as serial lines, you can change the actual bandwidth by adjusting hardware. For both classes of media, you can use the bandwidth configuration command to communicate the current bandwidth to the higher-level protocols.
IGRP uses the minimum path bandwidth to determine a routing metric. The TCP protocol adjusts initial retransmission parameters based on the apparent bandwidth of the outgoing interface.
At higher bandwidths, the value you configure with the bandwidth command is not what is displayed by the show interface command. The value shown is that used in IGRP updates and also used in computing load.
Note
Example
The following example sets the full bandwidth for DS3 transmissions:
interface serial 0 bandwidth 44736Related Commands
vines metric
cablelength
To specify the distance of the cable from the routers to the network equipment, use the cablelength controller configuration command. Use the no form of this command to restore the default cable length.
cablelength feet
no cablelengthSyntax Description
Default
224 feet for CT3IP interface processor.
50 feet for PA-T3 and PA-2T3 port adapters.
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
If you do not specify the cablelength command, the default cable length of 224 feet is used by the CT3IP.
If you do not specify the cablelength command, the default cable length of 50 feet is used by the PA-T3 and PA-2T3.
Note
Example
The following example sets the cable length for the router to 300:
controller t3 9/0/0cablelength 300cablelength long
To increase the pulse of a signal at the receiver and decrease the pulse from the transmitter using pulse equalization and line build-out for a T1 cable on an AS5200, use the cablelength long controller configuration command. Use the no form of this command, to return the pulse equalization and line build-out values to their default settings.
cablelength long dbgain-value dbloss-value {gain26 | gain36} {-15db | -22.5db | -7.5db | 0db}
no cablelength longSyntax Description
Default
Gain of 26 dB, and transmitter loss of 0 dB.
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2. The following choices were added in Cisco IOS Release 11.3 MA: gain26, gain36, -15db, -22.5db, -7.5db, and 0db.
Use this command for configuring the controller T1 interface on the AS5200 access server or on the Cisco MC3810 multiservice access concentrator, the cablelength long command is used to configure DS1 links (meaning, to build CSU/DSU links) when the cable length is no longer than 655 feet. On the Cisco MC3810, this command is supported on T1 controllers only.
On the Cisco MC3810, this command applies to Voice over Frame Relay, Voice over ATM, and Voice over HDLC.
Note
A pulse equalizer regenerates a signal that has been attenuated and filtered by a cable loss. Pulse equalization does not produce a simple gain, but it filters the signal to compensate for complex cable loss. A gain26 receiver gain compensates for a long cable length equivalent to 26 dB of loss, while a gain36 compensates for 36 dB of loss.
The lengthening or building out of a line is used to control far-end crosstalk. Line build-out attenuates the stronger signal from the customer installation transmitter so that the transmitting and receiving signals have similar amplitudes. A signal difference of less than 7.5 dB is ideal. Line build-out does not produce simple flat loss (also known as resistive flat loss). Instead, it simulates a cable loss of 7.5 dB, 15 dB, or 22.5 dB so that the resulting signal is handled properly by the receiving equalizer at the other end.
Example
The following example increases the receiver gain by 26 decibels and decreases the transmitting pulse by 7.5 decibels for a long cable:
AS5200(config)# controller t1 0AS5200(config-controller)# cablelength long gain26 -7.5dbThe following example configures the cable length for controller T1 0 on a Cisco MC3810 to a decibel pulse gain of 36 and a decibel pulse rate of -22.5 decibels:
MC3810(config)# controller t1 0MC3810(config)# cablelength long gain36 -22.5dbRealated Commands
cablelength short
cablelength short
To set a cable length 655 feet or shorter for a DS1 link on the Cisco MC3810, use the cablelength short controller configuration command. This command is supported on T1 controllers only. The no form of this command deletes the cablelength short value. To set cable lengths longer than 655 feet, use the cablelength long command.
cablelength short {133 | 266 | 399 | 533 | 655}
no cablelength shortSyntax Description
Default
133 feet.
Command Mode
Controller configuration mode
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3 MA and 11.3(2)AA.
On the Cisco MC3810, the cablelength short command is used to configure DSX-1 links when the cable length is 655 feet or less than 655 feet. On the Cisco MC3810, this command is supported on T1 controllers only.
Note
Example
In the following example, the cable length is set to 266 for the T1 controller in slot 0 on dial shelf 0:
router# configure terminalrouter(config)# controller t1 1/1/0router(config-controller)# cablelength short 266router (config-controller)# exitrouter(config)# exitrouter#Related Commands
cablelength long
cas-group
To configure channelized T1 timeslots with channel associated signaling (also known as robbed bit signaling), which enables an AS5200 modem to answer and send an analog call, use the cas-group controller configuration command. Use the no form of this command to disable channel associated signaling for one or more timeslots.
cas-group channel-number [timeslots range]
no cas-group channel-number [timeslots range]Syntax Description
Default
Disabled
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2.
Use this command to enable an AS5200 modem to receive and send incoming and outgoing analog calls through each T1 controller that is configured for a channelized T1 line, which has 24 possible channels.
Switched 56 digital calls are not supported under this new feature.
Example
The following example configures all 24 channels to support robbed bit signaling on a Cisco AS5200:
AS5200(config)# controller T1 0AS5200(config-controller)# cas-group 1 timeslots 1-24AS5200(config-controller)#%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 1 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 2 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 3 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 4 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 5 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 6 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 7 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 8 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 9 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 10 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 11 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 12 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 13 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 14 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 15 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 16 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 17 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 18 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 19 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 20 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 21 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 22 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 23 is up%DSX0-5-RBSLINEUP: RBS of controller 1 timeslot 24 is upchannel-group (Fast EtherChannel)
To assign a Fast Ethernet interface to a Fast EtherChannel group, use the channel-group interface configuration command. To remove a Fast Ethernet interface from a Fast EtherChannel group, use the no form of this command.
channel-group channel-number
no channel-group channel-numberSyntax Description
channel-number
Port-channel number previously assigned to the port-channel interface when using the interface port-channel global configuration command. The range is 1 to 4.
Default
No channel group is assigned.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
Before you assign a Fast Ethernet interface to a Fast EtherChannel group, you must first create a port-channel interface. To create a port-channel interface, use the interface port-channel global configuration command.
If the Fast Ethernet interface has an IP address assigned, you must disable it before adding the Fast Ethernet interface to the Fast EtherChannel. To disable an existing IP address on the Fast Ethernet interface, use the no ip address interface configuration command.
The Fast EtherChannel feature allows multiple Fast Ethernet point-to-point links to be bundled into one logical link to provide bidirectional bandwidth of up to 800 Mbps. Fast EtherChannel can be configured between Cisco 7500 series routers and Cisco 7000 series routers with the 7000 Series Route Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI) or between a Cisco 7500 series router or a Cisco 7000 series router with the RSP7000 and RSP700CI and a Catalyst 5000 switch.
Up to four Fast Ethernet interfaces can be added to a Fast EtherChannel group.
Caution
To display information about the Fast EtherChannel, use the show interfaces port-channel EXEC command.
Example
The following example adds Fast Ethernet 1/0 to the Fast EtherChannel group specified by port-channel 1:
Router(config)# interface port-channel 1Router(config-if)# ip address 1.1.1.10 255.255.255.0Router(config)# interface fastethernet 1/0/0Router(config-if)# channel-group 1Related Commands
interface port-channel
show interfaces port-channelclear controller lex
To reboot the LAN Extender chassis and restart its operating software, use the clear controller lex privileged EXEC command.
clear controller lex number [prom]
clear controller lex slot/port [prom] (for Cisco 7500 series routers)
clear controller lex [type slot/port] (Cisco 7200 series and for the Cisco 7500 series
with a Packet over SONET Interface Processor)
clear controller lex [type slot/port-adapter/port] (for Cisco 7500 series with ports on VIP cards)Syntax Description
number
Number of the LAN Extender interface corresponding to the LAN Extender to be rebooted.
prom
(Optional) Forces a reload of the PROM image, regardless of any Flash image.
slot
Refer to the appropriate hardware manual for slot and port information.
port
Refer to the appropriate hardware manual for slot and port information.
type
(Optional) Specifies the interface type. See Table 1 for keywords.
port-adapter
Refer to the appropriate hardware manual for information about port adapter compatibility.
Command Mode
Privileged EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
The clear controller lex command halts operation of the LAN Extender and performs a cold restart.
Without the prom keyword, if an image exists in Flash memory, and that image has a newer software version than the PROM image, and that image has a valid checksum, then this command runs the Flash image. If any one of these three conditions is not met, this command reloads the PROM image.
With the prom keyword, this command reloads the PROM image, regardless of any Flash image.
Examples
The following example halts operation of the LAN Extender bound to LAN Extender interface 2 and causes the LAN Extender to perform a cold restart from Flash memory:
Router#clear controller lex 2reload remote lex controller? [confirm] yesThe following example halts operation of the LAN Extender bound to LAN Extender interface 2 and causes the LAN Extender to perform a cold restart from PROM:
Router#clear controller lex 2 promreload remote lex controller? [confirm] yesclear counters
To clear the interface counters, use the clear counters EXEC command.
clear counters [type number]
clear counters [type slot/port] [ethernet | serial] (for the Cisco 4000 series or Cisco 7500 series
routers and a LAN Extender interface)
clear counters [type slot/port] (for Cisco 7200 series, and for the Cisco 7500 with a Packet
over SONET Interface Processor)
clear counters [type slot/port-adapter/port] (for Cisco 7500 series with ports on VIP cards)Syntax Description
type
(Optional) Specifies the interface type; one of the keywords listed in Table 1.
number
(Optional) Specifies the interface counter displayed with the show interfaces command.
ethernet
(Optional) If the type is lex, you can clear the interface counters on the Ethernet interface.
serial
(Optional) If the type is lex, you can clear the interface counters on the serial interface.
slot
Refer to the appropriate hardware manual for slot and port information.
port
Refer to the appropriate hardware manual for slot and port information.
port-adapter
Refer to the appropriate hardware manual for information about port adapter compatibility.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command was modified in Cisco IOS Release 11.3 to include the vg-anylan interface type keyword and to change the posi keyword to pos.
This command clears all the current interface counters from the interface unless the optional arguments type and number are specified to clear only a specific interface type (serial, Ethernet, Token Ring, and so on). Table 1 lists the command keywords and their descriptions.
Note
Examples
The following example clears all interface counters:
clear countersThe following example clears the Packet OC-3 interface counters on a POSIP card in slot 1 on a Cisco 7500 series router:
clear counters pos 1/0The following example clears interface counters on the serial interface residing on a Cisco 1000 series LAN Extender:
clear counters lex 0 serialThe following example clears the interface counters on a Fast Etherchannel interface.
Router# clear counter port-channel 1Clear "show interface" counters on all interfaces [confirm]%CLEAR-5-COUNTERS: Clear counter on all interfaces by console 1Related Commands
show interfaces
show interfaces port-channelclear hub
Use the clear hub EXEC command to reset and reinitialize the hub hardware connected to an interface of a Cisco 2505 or 2507 router.
clear hub ethernet number
ethernet
Indicates the hub in front of an Ethernet interface.
number
Hub number to clear, starting with 0. Since there is currently only one hub, this number is 0.
Syntax Description
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
Example
The following example clears hub 0:
clear hub ethernet 0Related Commands
hub
clear hub counters
Use the clear hub counters EXEC command to set to zero the hub counters on an interface of a Cisco 2505 or 2507 router.
clear hub counters [ether number [port [end-port]]]
Syntax Description
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
Example
The following example clears the counters displayed in a show hub command for all ports on hub 0:
clear hub counters ether 0Related Commands
show hub
clear interface
Use the clear interface EXEC command to reset the hardware logic on an interface.
clear interface type number
clear interface type slot/port (Cisco 7200, and 7500 series routers with a
Packet OC-3 Interface Processor)
clear interface [type slot/port-adapter/port] (ports on VIP cards in Cisco 7500 series routers)
clear interface type slot/port [:channel-group] (Cisco 7500 series routers)
clear interface type slot/port-adapter/port [:t1-channel] (CT3IP in Cisco 7500 series routers)Syntax Description
type
Specifies the interface type; it is one of the keywords listed in Table 1 in the "Usage Guidelines" section.
number
Specifies the port, connector, or interface card number.
slot
Refer to the appropriate hardware manual for slot and port information.
port
Refer to the appropriate hardware manual for slot and port information.
port-adapter
Refer to the appropriate hardware manual for information about port adapter compatibility.
:channel-group
(Optional) On Cisco 7500 series routers supporting channelized T1, specifies the channel from 0 to 23. This number is preceded by a colon.
:t1-channel
(Optional) For the CT3IP, the T1 channel is a number between 1 and 28.
T1 channels on the CT3IP are numbered 1 to 28 rather than the more traditional zero-based scheme (0 to 27) used with other Cisco products. This numbering scheme ensures consistency with telco numbering schemes for T1 channels within channelized T3 equipment.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command was modified in Cisco IOS Release 11.3 to include the vg-anylan interface type keyword and to change the posi keyword to pos.
Under normal circumstances, you do not need to clear the hardware logic on interfaces.
This command clears all the current interface hardware logic unless the optional arguments type and number are specified to clear only a specific interface type (serial, Ethernet, Token Ring, and so on). Table 2 lists the command keywords and their descriptions.
Examples
The following example resets the interface logic on HSSI interface 1:
clear interface hssi 1The following example resets the interface logic on Packet OC-3 interface 0 on the POSIP in slot 1:
clear interface pos 1/0The following example resets the interface logic on T1 0 on the CT3IP in slot 9:
clear interface serial 9/0/0:0The following example resets the interface logic on Fast Etherchannel interface 1:
Router# clear interface port-channel 1clear interface fastethernet
Use the clear interface fastethernet privileged EXEC command to reset the controller for a specified Fast Ethernet interface.
clear interface fastethernet number (Cisco 4500 and 4700 series routers)
clear interface fastethernet slot/port (Cisco 7200 and Cisco 7500 series routers)
clear interface fastethernet slot/port-adapter/port (Cisco 7500 series routers)Syntax Description
Command Mode
Privileged EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2.
Examples
The following example resets the controller for the FastEthernet 0 interface on a Cisco 4500:
clear interface fastethernet 0The following example resets the controller for the FastEthernet interface located in slot 1 port 0 on a Cisco 7200 series routers or Cisco 7500 series routers:
clear interface fastethernet 1/0The following example resets the controller for the FastEthernet interface located in slot 1 port adapter 0 port 0 on a Cisco 7500 series routers:
clear interface fastethernet 1/0/0clear rif-cache
Use the clear rif-cache EXEC command to clear entries from the Routing Information Field (RIF) cache.
clear rif-cache
Syntax Description
This command has no arguments or keywords.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Example
The following example clears the RIF cache:
clear rif-cacheRelated Commands
multiring
clear service-module serial
Use the clear service-module serial privileged EXEC configuration command to reset an integrated CSU/DSU.
clear service-module serial number
Syntax Description
Command Mode
Privileged EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2.
Use this command only in severe circumstances (for example, when the router is not responding to a CSU/DSU configuration command).
This command terminates all DTE and line loopbacks that are locally or remotely configured. It also interrupts data transmission through the router for up to 15 seconds. The software performs an automatic software reset in case of two consecutive configuration failures.
The CSU/DSU module is not reset with the clear interface command.
Caution
Example
The following example resets the CSU/DSU on a router:
router# clear service-module serial 0router#Related Commands
clear counters
test service-moduleclock rate
Use the clock rate interface configuration command to configure the clock rate for the hardware connections on serial interfaces such as network interface modules (NIMs) and interface processors to an acceptable bit rate. Use the no form of this command to remove the clock rate if you change the interface from a DCE to a DTE device. Using the no form of this command on a DCE interface sets the clock rate to the hardware-dependent default value.
clock rate bps
no clock rateSyntax Description
Default
No clock rate is configured.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command was modified in Cisco IOS Release 11.3 to include nonstandard clock rates for the PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+ synchronous serial port adapters.
Cable Length
Be aware that the fastest speeds might not work if your cable is too long, and that speeds faster than 148,000 bits per second are too fast for EIA/TIA-232 signaling. It is recommended that you only use the synchronous serial EIA/TIA-232 signal at speeds up to 64,000 bits per second. To permit a faster speed, use EIA/TIA-449 or V.35.
Synchronous Serial Port Adapters
For the synchronous serial port adapters (PA-8T-V35, PA-8T-X21, PA-8T-232, and PA-4T+) on Cisco 7200 series routers, and on second-generation Versatile Interface Processors (VIP2s) in Cisco 7500 series routers, the clock rate you enter is rounded (if needed) to the nearest value that your hardware can support. To display the clock rate value for the port adapter, use the more system:running-config command.
If you plan to netboot your router over a synchronous serial port adapter interface and have a boot image prior to Cisco IOS Release 11.1(9)CA that does not support nonstandard (rounded) clock rates for the port adapters, you must use one of the following standard clock rates:
1200, 2400, 4800, 9600, 19200, 38400, 56000, 64000
Examples
The following example sets the clock rate on the first serial interface to 64,000 bits per second:
interface serial 0clock rate 64000The following example sets the clock rate on a synchronous serial port adapter in slot 5, port 0 to 1234567. In this example, the clock rate is adjusted to 1151526 bps.
interface serial 5/0clock rate 1234567%Clockrate rounded to nearest value that your hardware can support.%Use Exec Command `more system:running-config' to see the value rounded to.The following example configures serial interface 5/0 with a clock rate that is rounded to the nearest value that is supported by the hardware:
Router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.Router(config)# interface serial 5/0Router(config-if)# clock rate 1234567%Clockrate rounded to nearest value that your hardware can support.%Use Exec Command `more system:running-config' to see the value rounded to.Router(config-if)# exitRouter(config)#The following example shows how to determine the exact clock rate that the serial interface was rounded to using the more system:running-config command. This example shows only the relevant information displayed by the more system:running-config command; other information was omitted.
Router# more system:running-configBuilding configuration......!interface Serial5/0no ip addressclockrate 1151526!...clock source (CT3IP)
Use the clock source controller configuration command to specify where the clock source is obtained for use by the Channelized T3 Interface Processor (CT3IP) in Cisco 7500 series routers. Use the no form of this command to restore the default clock source.
clock source {internal | line | loop-timed}
no clock sourceSyntax Description
Default
Internal
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
If you do not specify the clock source command, the default clock source of internal is used by the CT3IP.
You can also set the clock source for each T1 channel by using the t1 clock source controller configuration command.
Note
Example
The following example sets the clock source for the CT3IP to line:
controller t3 9/0/0clock source lineRelated Commands
t1 clock source
clock source (Cisco AS5200)
Use the clock source interface configuration command to select the clock source for the time-division multiplexing (TDM) bus in a Cisco AS5200 access server. The no form of this command configures the clock source to its default setting.
clock source {line {primary | secondary} | internal}
no clock source line {primary | secondary}Syntax Description
Defaults
Primary TDM clock source from the T1 0 controller
Secondary TDM clock source from the T1 1 controller
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2.
To use the clocking coming in from a T1 line, configure the clock source line primary command on the T1 interface that has the most reliable clocking. Configure the clock source line secondary command on the T1 interface that has the next best known clocking. With this configuration, the primary line clocking is backed up to the secondary line if the primary clocking shuts down.
Example
The following example configures the Cisco AS5200 access server to use T1 controller 0 as the primary clock source and T1 controller 1 as the secondary clock source:
controller t1 0clock source line primarycontroller t1 1clock source line secondaryclock source (Cisco MC3810)
To specify the clock source of a DS1 link on the Cisco MC3810, use the clock source controller configuration command .
clock source {line | internal | loop-timed}
Syntax Description
Default
Line (when the MFT is installed)
Internal (when the DVM is installed)
Command Mode
Controller configuration mode
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
This command applies to Voice over Frame Relay, Voice over ATM, and Voice over HDLC on the Cisco MC3810.
Example
The following example sets the clock source for controller T1 0 on the Cisco MC3810 to loop-timed.
controller T1 0 clock source loop-timed
Note
clock source (controller)
Use the clock source controller configuration command to set the T1-line clock-source for the MIP in the Cisco 7200 series and Cisco 7500 series or for the NPM in the Cisco 4000 series or a T3 interface or a PA-T3 serial port adapter.
clock source {line | internal}
Syntax Description
Defaults
Primary TDM clock source from the T0 controller
Secondary TDM clock source from the T1 controller
The line's receive data stream from the PA-T3 serial port adapter
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3
This command was modified in Cisco IOS Release 11.1 CA to include the T3 serial port adapter and PA-T3 serial port adapter.
This command applies to a Cisco 4000 router or Cisco 7000 series, Cisco 7200 series, and Cisco 7500 series router. A T3 interface on a PA-T3 serial port adapter can clock its transmitted data from either its internal clock or from a clock recovered from the line's receive data stream.
To use the clocking coming in from a T1 line, configure the clock source line primary command on the controller that has the most reliable clocking. Configure the clock source line secondary command on the controller that has the next best known clocking. With this configuration, the primary line clocking is backed up to the secondary line if the primary clocking shuts down.
Examples
The following example configures the Cisco AS5200 to use the T0 controller as the primary clocking source and the T1 controller as the secondary clocking source:
AS5200(config)# controller t1 0AS5200(config-if)# clock source line primaryAS5200(config-if)# exitAS5200(config)# controller t1 1AS5200(config-if)# clock source line secondaryThe following example specifies the T3 interface to clock its transmitted data from its internal clock:
interface serial 1/0clock source internalRelated Commands
framing
linecodeclock source (interface)
To control the clock used by a G.703-E1 interface, an E1-G.703/G.704 serial port adapter, or a PA-E3 serial port adapter will use to clock its transmitted data from, use the clock source interface configuration command. Use the no form of this command, to restore the default value.
Cisco 4000 Series and Cisco 7000 Series
clock source {line | internal}
no clock source
Cisco AS5200 Access Servers
clock source {line {primary | secondary} | internal}
no clock source line {primary | secondary}
Syntax Description
Default
By default, the applique uses the line's receive data stream.
Primary TDM clock source from the T0 controller on the Cisco AS5200.
Secondary TDM clock source from the T1 controller on the Cisco AS5200.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
This command was modified in Cisco IOS Release 11.1 CA to include the E1-G.703/G.704 serial port adapter, Pa-E3 serial port adapters, and Cisco 7200 series routers.
This command applies to a Cisco 4000 series, Cisco 7000 series, Cisco 7200 series, and Cisco 7500 series router. A G.703-E1 interface, E1-G.703/G.704 serial port adapter, or a PA-E3 serial port adapter can clock its transmitted data from either its internal clock or from a clock recovered from the line's receive data stream.
To use the clocking coming in from a T1 line for the Cisco AS5200, configure the clock source line primary command on the controller that has the most reliable clocking. Configure the clock source line secondary command on the controller that has the next best known clocking. With this configuration, the primary line clocking is backed up to the secondary line if the primary clocking shuts down.
Examples
The following example specifies the G.703-E1 interface to clock its transmitted data from its internal clock:
interface serial 0/1clock source internalThe following example configures the Cisco AS5200 to use the T0 controller as the primary clocking source and the T1 controller as the secondary clocking source:
AS5200(config)# controller t1 0AS5200(config-if)# clock source line primaryAS5200(config-if)# exitAS5200(config)# controller t1 1AS5200(config-if)# clock source line secondarycmt connect
Use the cmt connect EXEC command to start the processes that perform the connection management (CMT) function and allow the ring on one fiber to be started.
cmt connect [interface-name phy-a | phy-b]]
Syntax Description
interface-name
(Optional) Specifies the FDDI interface.
phy-a
(Optional) Selects Physical Sublayer A.
phy-b
(Optional) Selects Physical Sublayer B.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
In normal operation, the FDDI interface is operational once the interface is connected and configured. The cmt connect command allows the operator to start the processes that perform the CMT function.
The cmt connect command is not needed in the normal operation of FDDI; this command is used mainly in interoperability tests.
Examples
The following examples demonstrate use of the cmt connect command for starting the CMT processes on the FDDI ring.
The following command starts all FDDI interfaces:
cmt connectThe following command starts both fibers on the FDDI interface unit 0:
cmt connect fddi 0The following command on the Cisco 7200 series or Cisco 7500 series starts both fibers on the FDDI interface unit 0:
cmt connect fddi 1/0The following command starts only Physical Sublayer A on the FDDI interface unit 0:
cmt connect fddi 0 phy-aThe following command on Cisco 7500 series routers starts only Physical Sublayer A on the FDDI interface unit 0:
cmt connect fddi 1/0 phy-acmt disconnect
Use the cmt disconnect EXEC command to stop the processes that perform the connection management (CMT) function and allow the ring on one fiber to be stopped.
cmt disconnect [interface-name [phy-a | phy-b]]
Syntax Description
interface-name
(Optional) Specifies the FDDI interface.
phy-a
(Optional) Selects Physical Sublayer A.
phy-b
(Optional) Selects Physical Sublayer B.
Command Mode
EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
In normal operation, the FDDI interface is operational once the interface is connected and configured, and is turned off using the shutdown interface configuration command. The cmt disconnect command allows the operator to stop the processes that perform the CMT function and allow the ring on one fiber to be stopped.
The cmt disconnect command is not needed in the normal operation of FDDI; this command is used mainly in interoperability tests.
Examples
The following examples demonstrate use of the cmt disconnect command for stopping the CMT processes on the FDDI ring.
The following command stops all FDDI interfaces:
cmt disconnectThe following command stops both fibers on the FDDI interface unit 0:
cmt disconnect fddi 0The following command on the Cisco 7200 series or Cisco 7500 series stops both fibers on the FDDI interface unit zero:
cmt disconnect fddi 1/0The following command stops only Physical Sublayer A on the FDDI interface unit 0. This command causes the FDDI media to go into a wrapped state so that the ring will be broken.
cmt disconnect fddi 0 phy-aThe following command on the Cisco 7500 series stops only Physical Sublayer A on the FDDI interface unit 0 in slot 1. This command causes the FDDI media to go into a wrapped state so that the ring will be broken.
cmt disconnect fddi 1/0 phy-acompress
To configure compression for Link Access Procedure, Balanced (LAPB), Point-to-Point Protocol (PPP), and High-Level Data Link Control (HDLC) encapsulations, use the compress interface configuration command. On Cisco 7200 series routers and Cisco 7500 series routers, hardware compression on the compression service adapter (CSA) is supported for PPP links. To disable compression, use the no form of this command.
compress {predictor | stac}
no compress {predictor | stac}
Cisco VIP2 cards
compress {predictor | stac [distributed | software]}
Cisco 7200 Series
compress {predictor | stac [ csa slot | software]}
PPP Encapsulation
compress [predictor | stac | mppc [ignore-pfc]]
Syntax Description
Default
Compression is disabled.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0 (as compress predictor).
The command compress {predictor | stac} first appeared in Cisco IOS Release 10.3.
This command was modified in Cisco IOS Release 11.3 P to include the distributed, software, and csa keywords.
This command was modified in Cisco IOS Release 11.3 T to add the mppc and ignore-pfc options.
Using CSA hardware compression on Cisco 7200 series routers and Cisco 7500 series routers removes the compression and decompression responsibilities from the VIP2 or the main processor installed in the router. By using the compress stac command, the router determines the fastest compression method available on the router.
When using hardware compression on Cisco 7200 series routers with multiple CSAs, you can optionally specify which CSA is used by the interface to perform compression. If no CSA is specified, the router determines which CSA is used. On Cisco 7500 series routers, the router uses the CSA on the same VIP2 as the interface.
You can configure point-to-point software compression for all LAPB, PPP, and HDLC encapsulations. Compression reduces the size of frames via lossless data compression. HDLC encapsulations supports the Stacker compression algorithm. PPP and LAPB encapsulations support both predictor and Stacker compression algorithms.
When compression is performed in software installed in the router's main processor, it might significantly affect system performance. We recommend that you disable compression if the CPU load exceeds 40 percent. To display the CPU load, use the show process cpu EXEC command.
Compression requires that both ends of the serial link be configured to use compression.
If the majority of your traffic is already compressed files, we recommend that you not use compression. If the files are already compressed, the additional processing time spent in attempting unsuccessfully to compress them again will slow system performance.
Table 3 provides general guidelines for deciding which compression type to select.
Software compression makes heavy demands on the router's processor. The maximum compressed serial line rate depends on the type of Cisco router you are using and which compression algorithm you specify. Table 4 shows a summary of the compressed serial line rates for software compression. The maximums shown in Table 4 apply to the "combined" serial compressed load on the router. For example, a Cisco 4000 series router could handle four 64-kbps lines using Stacker or one 256-kbps line. These maximums also assume there is very little processor load on the router aside from compression. Lower these numbers when the router is required to do other processor-intensive tasks.
Hardware compression can support a combined line rate of 16 Mbps.
Cisco recommends that you do not adjust the maximum transmission unit (MTU) for the serial interface and the LAPB maximum bits per frame (N1) parameter.
Note
Examples
The following example enables hardware compression and PPP encapsulation on serial interface 3/1/0.
interface serial 3/1/0encapsulate pppcompress stacThe following example enables predictor compression on serial interface 0 for a LAPB link:
interface serial 0encapsulation lapbcompress predictorRelated Commands
encapsulation lapb
encapsulation ppp
encapsulation x25
ppp compress
show compress
show processescontroller t3
To configure the Channelized T3 Interface Processor (CT3IP) in Cisco 7500 series routers, use the controller t3 global configuration command.
controller t3 slot/port-adapter/port
Syntax Description
Default
No T3 controller is configured.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command is used to configure the CT3IP and the 28 T1 channels. After the T1 channels are configured, continue to configure each T1 channel as a serial interface by using the interface serial global configuration command.
Example
The following example configures the CT3IP in slot 3:
controller t3 3/0/0Related Commands
interface serial
copy flash lex
To download an executable image from Flash memory on the core router to the LAN Extender chassis, use the copy flash lex privileged EXEC command.
copy flash lex number
Syntax Description
Command Mode
Privileged EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
If you attempt to download a version of the software older than what is currently running on the LAN Extender, a warning message is displayed.
Example
The following example copies the executable image namexx to the LAN Extender interface 0:
Router# copy flash lex 0Name of file to copy? namexxAddress of remote host [255.255.255.255] <cr>writing namexx !!!!!!!!!!!!!!!!!!!!!!!!!copy completeRelated Commands
copy tftp lex
copy tftp lex
To download an executable image from a TFTP server to the LAN Extender, use the copy tftp lex privileged EXEC command.
copy tftp lex number
Syntax Description
Command Mode
Privileged EXEC
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
If you attempt to download a version of the software older than what is currently running on the LAN Extender, a warning message is displayed.
Example
The following example copies the file namexx from the TFTP server:
Router# copy tftp lex 0Address or name of remote host (255.255.255.255]? 131.108.1.111Name of file to copy? namexxOK to overwrite software version 1.0 with 1.1 ?[confirm]Loading namexx from 131.108.13.111!!!!!!!!!!!!!!!!!!!!!!!!![OK - 127825/131072 bytes]Successful download to LAN Extendercrc
To set the length of the cyclic redundancy check (CRC) on a Fast Serial Interface Processor (FSIP) or HSSI Interface Processor (HIP) of the Cisco 7500 series routers or on a 4-port serial adapter of the Cisco 7200 series routers, use the crc interface configuration command. To set the CRC length to 16 bits, use the no form of this command.
crc size
no crcSyntax Description
Default
16 bits
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
All interfaces use a 16-bit cyclic redundancy check (CRC) by default, but also support a 32-bit CRC. CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted data. The designators 16 and 32 indicate the length (in bits) of the frame check sequence (FCS). A CRC of 32 bits provides more powerful error detection, but adds overhead. Both the sender and receiver must use the same setting.
CRC-16, the most widely used throughout the United States and Europe, is used extensively with wide-area networks (WANs). CRC-32 is specified by IEEE 802 and as an option by some point-to-point transmission standards. It is often used on SMDS networks and LANs.
Example
The following example enables the 32-bit CRC on serial interface 3/0:
interface serial 3/0crc 32crc4
To enable generation of CRC4 (per ITU Recommendation G.704 and G.703) to improve data integrity, use the crc4 interface configuration command. To disable this feature, use the no form of this command.
crc4
no crc4Syntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
This command was modified in Cisco IOS Release 11.1 CA to include the Cisco 7200 series router and the E1-G.703/G.704 serial port adapter.
This command applies to a Cisco 4000 router, Cisco 7200 series, Cisco 7000 series, and Cisco 7500 series router. This command is supported on the FSIP and the E1-G.703/G.704 serial port adapter.
This command is useful for checking data integrity while operating in framed mode. CRC4 provides additional protection for a frame alignment signal under noisy conditions. For data transmission at E1 (2.048 Mbps), the G.704 standard suggests 4 bits CRC. Refer to CCITT Recommendation G.704 for a definition of CRC4.
You can also use the crc command to set the CRC size for the HDLC controllers.
Example
The following example enables CRC4 generation on the E1-G.703/G.704 serial port adapter and also sets the CRC size to 32 bits:
interface Serial 0/0crc 32crc4crc bits 5
To enable generation of CRC5 (per ITU Recommendation G.704 and G.703) to improve data integrity, use the crc bits 5 interface configuration command. To disable this feature, use the no form of this command.
crc bits 5
no crc bits 5Syntax Description
This command has no arguments or keywords.
Default
The default is no CRC5 checking.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
This command is available for the JT2 6.3-MHz serial port adapter (PA-2JT2) on second-generation Versatile Interface Processor (VIP2), in Cisco 7500 series routers, and in Cisco 7000 series routers with the 7000 Series Route Switch Processor (RSP7000) and 7000 Series Chassis Interface (RSP7000CI).
This command is useful for checking data integrity while operating in framed mode. CRC5 provides additional protection for a frame alignment signal under noisy conditions. For data transmission at JT2 (6.312 Mbps), the G.704 standard suggests 5 bits CRC. Refer to ITU Recommendation G.704 for a definition of CRC5.
You can also use the crc command to set the CRC size for the HDLC controllers.
Example
The following example enables CRC 5 generation on the PA-2JT2 port adapter and also sets the CRC size to 32 bits:
interface Serial 0/0crc 32crc bits 5cut-through
To configure the interfaces on the PA-12E/2FE port adapter to use cut-through switching technology between interfaces within the same bridge group, use the cut-through interface command. To return each interface to store-and-forward switching, use the no form of this command.
cut-through [receive | transmit]
no cut-throughSyntax Description
receive
(Optional) Selects cut-through switching technology on received data.
transmit
(Optional) Selects cut-through switching technology on transmitted data.
Default
Store-and-forward switching technology
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2 P.
Cut-through mode allows switched packets to be transmitted after 64 bytes are received. The transmission of the packets can start before the end of the packet arrives. This reduces the time spent in the switch, but allows packets to be transmitted with bad CRCs, because the transmission is initiated before the CRC is received or checked. Store-and-forward mode waits for the entire packet to be received before that packet is forwarded, but will check the CRC before starting transmission.
The PA-12E/2FE port adapter off-loads Layer 2 switching from the host CPU by using store-and-forward or cut-through switching technology between interfaces within the same virtual LAN (VLAN) on the PA-12E/2FE port adapter. The PA-12E/2FE port adapter supports up to four VLANs (bridge groups).
Example
The following example configures interface 3/0 for cut-through switching:
Router(config)#interface fastethernet 3/0Router(config-if)#bridge-group 10Router(config-if)#cut-throughRouter(config-if)#no shutdownRouter(config-if)# exitRouter(config)#Related Commands
more system:running-config
