Table Of Contents
half-duplex controlled-carrier
delay
To set a delay value for an interface, use the delay interface configuration command. Use the no form of this command to restore the default delay value.
delay tens-of-microseconds
no delaySyntax Description
tens-of-microseconds
Integer that specifies the delay in tens of microseconds for an interface or network segment.
Default
Default delay values may be displayed with the EXEC command show interfaces.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Example
The following example sets a 30,000-microsecond delay on serial interface 3:
interface serial 3 delay 30000Related Commands
show interfaces
dce-terminal-timing enable
When running the line at high speeds and long distances, use the dce-terminal-timing enable interface configuration command to prevent phase shifting of the data with respect to the clock. If SCTE is not available from the DTE, use no form of this command, which causes the DCE to use its own clock instead of SCTE from the DTE.
dce-terminal-timing enable
no dce-terminal-timing enableSyntax Description
This command has no keywords or arguments.
Default
DCE uses its own clock.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
On the Cisco 4000 platform, you can specify the serial Network Interface Module timing signal configuration. When the board is operating as a DCE and the DTE provides terminal timing (SCTE or TT), the dce-terminal-timing enable command causes the DCE to use SCTE from the DTE.
Example
The following example prevents phase shifting of the data with respect to the clock:
interface serial 0 dce-terminal-timing enabledescription (controller)
Use the description controller configuration command to add a description to an E1 or T1 controller or the Channelized T3 Interface Processor (CT3IP) in Cisco 7500 series routers. Use the no form of this command to remove the description.
description string
no descriptionSyntax Description
string
Comment or a description to help you remember what is attached to the interface. Up to 80 characters.
Default
No description is added.
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
This command was modified in Cisco IOS Release 11.3 to include the CT3IP controller.
The description command is meant solely as a comment to be put in the configuration to help you remember what certain controllers are used for. The description affects the CT3IP and MIP interfaces only and appears in the output of the show controller t3, show controller e1, show controller t1, and more system:running-config EXEC commands.
Example
The following example describes a 3174 controller:
controller t1description 3174 Controller for test labRelated Commands
show controller e1
show controller t1
show controller t3
more system:running-configdown-when-looped
Use the down-when-looped interface configuration command to configure an interface to inform the system it is down when loopback is detected.
down-when-looped
Syntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command is valid for HDLC or PPP encapsulation on serial and HSSI interfaces.
Backup Interfaces
When an interface has a backup interface configured, it is often desirable that the backup interface be enabled when the primary interface is either down or in loopback. By default, the backup is only enabled if the primary interface is down. By using the down-when-looped command, the backup interface will also be enabled if the primary interface is in loopback.
Testing an Interface with the Loopback Command
If testing an interface with the loopback command, or by placing the DCE into loopback, down-when-looped should not be configured; otherwise, packets will not be transmitted out the interface that is being tested.
Example
The following example configures interface serial 0 for HDLC encapsulation. It is then configured to let the system know that it is down when in loopback mode.
interface serial0encapsulation hdlcdown-when-loopedRelated Commands
backup interface serial
loopback (interface)dsu bandwidth
To specify the maximum allowable bandwidth used by the PA-E3 port adapter and PA-T3 port adapter, use the dsu bandwidth interface configuration command. To return to the default bandwidth, use the no form of this command.
dsu bandwidth kbps
no dsu bandwidthSyntax Description
kbps
Maximum bandwidth in the range of 22 kbps to 44736 kbps. The default varies for different port adapters.
Default
34010 kbps for PA-E3
44736 kbps for PA-T3
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
The local interface configuration must match the remote interface configuration. For example, if you reduce the maximum bandwidth to 16000 on the local port, you must also do the same on the remote port.
The dsu bandwidth command reduces the bandwidth by padding the E3 and T3 frame.
To verify the data service unit (DSU) bandwidth configured on the interface, use the show controller serial EXEC command.
Example
The following example sets the DSU bandwidth to 16000 kbps on interface 1/0/0:
interface serial 1/0/0dsu bandwidth 16000Related Commands
dsu mode
To specify the interoperability mode used by a PA-E3 port adapter or PA-T3 port adapter, use the dsu mode interface configuration command. To return to the default mode, use the no form of this command.
dsu mode {0 | 1 | 2}
no dsu modeSyntax Description
Default
0 mode
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
The local interface configuration must match the remote interface configuration. For example, if you define the data service unit (DSU) interoperability mode as 1 on the local port, you must also do the same on the remote port.
You must know what type of DSU is connected to the remote port to determine if it interoperates with a PA-E3 port adapter or a PA-T3 port adapter. Use mode 0 to connect a PA-E3 port adapter to another PA-E3 port adapter or to a Digital Link DSU (DL3100). Use mode 0 to connect a PA-T3 port adapter to another PA-T3 port adapter or to a Digital Link DSU (DL3100). Use mode 1 to connect a PA-E3 port adapter or a PA-T3 port adapter to a Kentrox DSU. Use mode 2 to connect a PA-T3 port adapter to a Larscom DSU. The dsu mode command enables and improves interoperability with other DSUs.
The dsu mode command enables and improves interoperability with other DSUs.
To verify the DSU mode configured on the interface, use the show controller serial EXEC command.
Example
The following example sets the DSU mode to 1 on interface 1/0/0:
interface serial 1/0/0dsu mode 1Related Commands
dte-invert-txc
Use the dte-invert-txc interface configuration command to invert the TXC clock signal received from the DCE. Use the no form of this command if the DCE accepts SCTE from the DTE.
dte-invert-txc
no dte-invert-txcSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Use this command if the DCE cannot receive SCTE from the DTE, the data is running at high speeds, and the transmission line is long. This prevents phase shifting of the data with respect to the clock.
On the Cisco 4000 series, you can specify the serial Network Processor Module timing signal configuration. When the board is operating as a DTE, the dte-invert-txc command inverts the TXC clock signal it gets from the DCE that the DTE uses to transmit data. If the DCE accepts SCTE from the DTE, use no dte-invert-txc.
Example
The following example inverts the TXC on serial interface 0:
interface serial 0 dte-invert-txcduplex
To configure the duplex operation on an interface, use the duplex interface configuration command. Use the no form of this command to return the system to half-duplex mode, which is the system default.
duplex {full | half | auto}
no duplexSyntax Description
Default
Half-duplex mode
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2(10)P.
To use the auto-negotiation capability (that is, detect speed and duplex modes automatically), you must set both speed and duplex to auto. Setting speed to auto negotiates speed only, and setting duplex to auto negotiates duplex only.
Table 1 describes the access server's performance for different combinations of the duplex and speed modes. The specified duplex command configured with the specified speed command produces the resulting system action.
For the Cisco AS5300, the duplex {full | half | auto} command syntax replaces the following two earlier duplex commands:
•
half-duplex
•
You will get the following error messages if you try to use these commands on a Cisco AS5300:
router(config)# interface fastethernet 0router(config-if)# full-duplexPlease use duplex command to configure duplex moderouter(config-if)#router(config-if)# half-duplexPlease use duplex command to configure duplex modeExample
The following example shows the different duplex configuration options you can configure on a Cisco AS5300:
router# configure terminalEnter configuration commands, one per line. End with CNTL/Z.router(config)# interface fastethernet 0router(config-if)# duplex ?auto Enable AUTO duplex configurationfull Force full duplex operationhalf Force half-duplex operationRelated Commands
duplex
interface fastethernet
show controller fastethernet
speedearly-token-release
To enable early token release on Token Ring interfaces, use the early-token-release interface configuration command. Once enabled, use the no form of this command to disable this feature.
early-token-release
no early-token-releaseSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Early token release is a method whereby the Token Ring interfaces can release the token back onto the ring immediately after transmitting, rather than waiting for the frame to return. This feature helps increase the total bandwidth of the Token Ring.
The Token Ring Interface Processor (TRIP) on the Cisco 7500 series routers and the Token Ring adapters on the Cisco 7200 series routers all support early token release.
Examples
The following example enables the use of early token release on Token Ring interface 1:
interface tokenring 1early-token-releaseOn the Cisco 7500 series, to enable the use of early token release on your Token Ring interface processor in slot 4 on port 1, issue the following configuration commands:
interface tokenring 4/1early-token-releaseencapsulation
To set the encapsulation method used by the interface, use the encapsulation interface configuration command.
encapsulation encapsulation-type
Syntax Description
Default
The default depends on the type of interface. For example, a synchronous serial interface defaults to HDLC.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
To use SLIP or PPP, the router or access server must be configured with an IP routing protocol or with the ip host-routing command. This configuration is done automatically if you are using old-style slip address commands. However, you must configure it manually if you configure SLIP or PPP via the interface async command.
Examples
The following example resets HDLC serial encapsulation on serial interface 1:
interface serial 1 encapsulation hdlcThe following example enables PPP encapsulation on serial interface 0:
interface serial 0encapsulation pppRelated Commands
keepalive
ppp
ppp authentication
slipfddi burst-count
Use the fddi burst-count interface configuration command to allow the FCI card to preallocate buffers to handle bursty FDDI traffic (for example, NFS bursty traffic). Use the no form of this command to revert to the default value.
fddi burst-count number
no fddi burst-countSyntax Description
Default
3 buffers
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command applies to the FCI card only. The microcode software version should not be 128.45 or 128.43.
Example
The following example sets the number of buffers to 5:
interface fddi 0 fddi burst-count 5fddi c-min
To set the C-Min timer on the PCM, use the fddi c-min interface configuration command. Use the no form of this command to revert to the default value.
fddi c-min microseconds
no fddi c-minSyntax Description
Default
1600 microseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.
Example
The following example sets the C-Min timer to 2000 microseconds:
interface fddi 0 fddi c-min 2000Related Commands
fddi tb-min
fddi tl-min-time
fddi t-outfddi cmt-signal-bits
To control the information transmitted during the connection management (CMT) signaling phase, use the fddi cmt-signal-bits interface configuration command.
fddi cmt-signal-bits signal-bits [phy-a | phy-b]
Syntax Description
signal-bits
A hexadecimal number preceded by 0x; for example, 0x208. The FDDI standard defines ten bits of signaling information that must be transmitted, as follows:
•
•
•
•
•
•
•
•
phy-a
(Optional) Selects Physical Sublayer A.
phy-b
(Optional) Selects Physical Sublayer B.
Defaults
The default signal bits for the phy-a and phy-b keywords are as follows:
•
•
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
If neither the phy-a nor phy-b keyword is specified, the signal bits apply to both physical connections.
Note
Table 2 lists the physical types.
Table 2 FDDI Physical Type Bit Specifications
0
0
Physical A
1
0
Physical B
0
1
Physical S
1
1
Physical M
Table 3 lists the duration bits.
Example
The following example sets the CMT signaling phase to signal bits 0x208 on both physical connections:
interface fddi 0 fddi cmt-signal-bits 208fddi duplicate-address-check
Use the fddi duplicate-address-check interface configuration command to turn on the duplicate address detection capability on the FDDI. Use the no form of this command to disable this feature.
fddi duplicate-address-check
no fddi duplicate-address-checkSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
If you use this command, the Cisco IOS software will detect a duplicate address if multiple stations are sharing the same MAC address. If the software finds a duplicate address, it will shut down the interface.
Example
The following example enables duplicate address checking on the FDDI:
interface fddi 0 fddi duplicate-address-checkfddi encapsulate
Use the fddi encapsulate interface configuration command to specify encapsulating bridge mode on the CSC-C2/FCIT interface card. Use the no form of this command to turn off encapsulation bridging and return the FCIT interface to its translational, nonencapsulating mode.
fddi encapsulate
no fddi encapsulateSyntax Description
This command has no arguments or keywords.
Default
The FDDI interface by default uses the SNAP encapsulation format defined in RFC 1042. It is not necessary to define an encapsulation method for this interface when using the CSC-FCI interface card.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The no fddi encapsulate command applies only to CSC-C2/FCIT interfaces, because the CSC-FCI interfaces are always in encapsulating bridge mode. The CSC-C2/FCIT interface card fully supports transparent and translational bridging for the following configurations:
•
•
•
The command fddi encapsulate puts the CSC-C2/FCIT interface into encapsulation mode when doing bridging. In transparent mode, the FCIT interface interoperates with earlier versions of the CSC-FCI encapsulating interfaces when performing bridging functions on the same ring.
Caution
The following protocols have problems when bridged between Token Ring and other media: Novell IPX, DECnet Phase IV, AppleTalk, VINES, XNS, and IP. Further, the following protocols may have problems when bridged between FDDI and other media: Novell IPX and XNS. We recommend that these protocols be routed whenever possible.
Example
The following example sets FDDI interface 1 on the CSC-C2/FCIT interface card to encapsulating bridge mode:
interface fddi 1 fddi encapsulatefddi frames-per-token
To specify the maximum number of frames that the FDDI interface will transmit per token capture, use the fddi frames-per-token interface configuration command. Us the no form of this command to revert to the default value.
fddi frames-per-token number
no fddi frames-per-tokenSyntax Description
number
Maximum number of frames to transmit per token capture. Valid values are from 1 to 10. the default is 3.
Default
3 frames
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2 P.
Changing the value will increase or decrease the maximum number of frames that the FDDI interface can transmit when it receives a token. Increasing the value does not necessarily mean more frames will be transmitted on each token capture. This is heavily dependent on the traffic load of the specific interface.
When the interface captures a token, it transmits all of the frames that are queued in the interface's transmit ring, up to a maximum value specified by the fddi frames-per-token command.
If there are no frames ready for transmission, the token is passed on, and no frames are transmitted. If there are less than the fddi frames-per-token value in the transmit ring, all frames in the transmit ring are transmitted before the token is passed on. If there are more than the fddi frames-per-token value in the transmit ring, the specified value is transmitted before the token is passed on. The remaining frames in the transmit ring remain queued until the token is captured again.
Example
The following example shows how to configure the FDDI interface to transmit four frames per token capture:
! Show fddi frames-per-token command options4700(config-if)#fddi frames-per-token ?<1-10> Number of frames per token, default = 3! Specify 4 as the maximum number of frames to be transmitted per token4700(config-if)#fddi frames-per-token 4fddi smt-frames
To enable the SMT frame processing capability on the FDDI, use the fddi smt-frames interface configuration command. Use the no form of this command to disable this function and prevent the Cisco IOS software from generating or responding to SMT frames.
fddi smt-frames
no fddi smt-framesSyntax Description
This command has no arguments or keywords.
Default
Enabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Use the no form of this command to turn off SMT frame processing for diagnosing purposes. Use the fddi smt-frames command to reenable the feature.
Example
The following example disables SMT frame processing:
interface fddi 0 no fddi smt-framesfddi tb-min
To set the TB-Min timer in the physical connection management (PCM), use the fddi tb-min interface configuration command. Use the no form of this command to revert to the default value.
fddi tb-min milliseconds
no fddi tb-minSyntax Description
Default
100 milliseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.
Example
The following example sets the TB-Min timer to 200 milliseconds:
interface fddi 0 fddi tb-min 200Related Commands
fddi c-min
fddi tl-min-time
fddi t-outfddi tl-min-time
To control the TL-Min time (the minimum time to transmit a Physical Sublayer, or PHY line state, before advancing to the next physical connection management [PCM] state, as defined by the X3T9.5 specification), use the fddi tl-min-time interface configuration command.
fddi tl-min-time microseconds
Syntax Description
Default
30 microseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Interoperability tests have shown that some implementations of the FDDI standard need more than 30 microseconds to sense a signal.
Examples
The following example changes the TL-Min time from 30 microseconds to 100 microseconds:
interface fddi 0fddi tl-min-time 100The following example changes the TL-Min time from 30 microseconds to 100 microseconds on a Cisco 7500 series router:
interface fddi 3/0fddi tl-min-time 100Related Commands
fddi c-min
fddi tl-min-time
fddi t-outfddi t-out
To set the t-out timer in the physical connection management (PCM), use the fddi t-out interface configuration command. Use the no form of this command to revert to the default value.
fddi t-out milliseconds
no fddi t-outSyntax Description
Default
100 milliseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
This command applies to the processor CMT only. You need extensive knowledge of the PCM state machine to tune this timer. Use this command when you run into PCM interoperability problems.
Example
The following example sets the timeout timer to 200 milliseconds:
interface fddi 0fddi t-out 200Related Commands
fddi c-min
fddi tb-min
fddi tl-min-timefddi token-rotation-time
To control ring scheduling during normal operation and to detect and recover from serious ring error situations, use the fddi token-rotation-time interface configuration command.
fddi token-rotation-time microseconds
Syntax Description
microseconds
Number that specifies the token rotation time (TRT). The default is 5,000 microseconds.
Default
5000 microseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The FDDI standard restricts the allowed time to be greater than 4000 microseconds and less than 165,000 microseconds. As defined in the X3T9.5 specification, the value remaining in the TRT is loaded into the token holding timer (THT). Combining the values of these two timers provides the means to determine the amount of bandwidth available for subsequent transmissions.
Examples
The following example sets the rotation time to 24,000 microseconds:
interface fddi 0fddi token-rotation-time 24000The following example sets the rotation time to 24,000 microseconds on a Cisco 7500 series router:
interface fddi 3/0fddi token-rotation-time 24000fddi valid-transmission-time
To recover from a transient ring error, use the fddi valid-transmission-time interface configuration command.
fddi valid-transmission-time microseconds
Syntax Description
microseconds
Number that specifies the transmission valid timer (TVX) interval. The default is 2,500 microseconds.
Default
2,500 microseconds
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Examples
The following example changes the transmission timer interval to 3000 microseconds:
interface fddi 0fddi valid-transmission-time 3000The following example changes the transmission timer interval to 3000 microseconds on a Cisco 7000 series routers or Cisco 7200 series routers:
interface fddi 3/0fddi valid-transmission-time 3000fdl
To set the facilities data link exchange standard for the CSU controllers, enter the fdl controller configuration command. Use the no form of this command, to disables facilities data-link support.
fdl {att | ansi | both}
no fdl {att | ansi | both}Syntax Description
Default
Disabled
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
This command was modified in Cisco IOS Release 12.0, to add command syntax both for the MC3810.
You must configure this command on both T1 controllers if you want to support the CSU function on each T1 line. However, you must use the same facilities data link exchange standard as your service provider. You can have a different standard configured on each T1 controller.
Example
The following example configures the ANSI T1.403 standard for both T1 controllers:
Router(config)# controller t1 0Router(config-controller)# fdl ansiRouter(config-controller)# exitRouter(config)# controller t1 1Router(config-controller)# fdl ansiframing (E1/T1 controller)
Use the framing controller configuration command to select the frame type for the E1 or T1 data line.
framing {sf | esf} (for T1 lines)
framing {crc4 | no-crc4} [australia] (for E1 lines)Syntax Description
Defaults
Super frame is the default on a T1 line.
CRC4 frame is the default on an E1 line.
Command Mode
Controller configuration
Usage Guidelines
Use this command in configurations where the router or access server is intended to communicate with T1 or E1 fractional data line. The service provider determines which framing type, either sf, esf, or crc4, is required for your T1/E1 circuit.
Example
The following example selects extended super frame as the T1 frame type:
framing esfRelated Commands
cablelength
linecodeframing (E3/T3 interface)
To specify E3 or T3 line framing for a PA-E3 port adapter or PA-T3 port adapter, use the framing interface configuration command. To return to the default G.751 framing or C-bit framing, use the no form of this command.
framing {bypass | g751} (PA-E3)
framing {c-bit | m13 | bypass} (PA-T3)
no framingSyntax Description
Default
G.751 framing for PA-E3
C-bit framing for PA-T3
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
The default framing is described in the ITU-T Recommendation G.751.
Note
When the framing mode is bypass, the E3 frame data is not included in the E3 frame, just the data.
When the framing mode is bypass, the T3 frame data is not included in the T3 frame, just the data.
If you use the bypass option, scrambling must be set to the default (disabled), the dsu mode must be set to the default (0), and the dsu bandwidth must be set to the default (44736).
To verify the framing mode configured on the interface, use the show controller serial EXEC command.
Example
The following example sets the framing mode to bypass on interface 1/0/0:
interface serial 1/0/0framing bypassRelated Command
framing (T3 controller)
To specify T3 line framing used by the CT3IP port adapter, use the framing controller configuration command. Use the no form of this command to restore the default framing type.
framing {c-bit | m23 | auto-detect}
no framingSyntax Description
Default
auto-detect for CT3IP
Command Mode
Controller configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1 CA.
If you do not specify the framing command, the default auto-detect is used by the CT3IP to automatically determine the framing type received from the far-end equipment.
Because the CT3IP supports the Application Identification Channel (AIC) signal, the setting for the framing might be overridden by the CT3IP firmware.
You can also set the framing for each T1 channel by using the t1 framing controller configuration command.
Example
The following example sets the framing for the CT3IP to C-bit:
controller t3 9/0/0framing c-bitRelated Commands
full-duplex
To specify full-duplex mode on full-duplex single-mode and multimode port adapters, use the full-duplex interface configuration command. Use the no form of this command to restore the default half-duplex mode.
full-duplex
no full-duplexSyntax Description
This command has no arguments or keywords.
Default
Half-duplex mode is the default mode on a Cisco 7500 series router and a FEIP.
Half-duplex mode is the default mode for serial interfaces that are configured for bisynchronous tunneling.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
This command was modified in Cisco IOS Release 11.3 to include information on FDDI full-duplex, single-mode and multimode port adapters.
Use this command if the equipment on the other end is capable of full-duplex mode.
This command specifies full-duplex mode on full-duplex single-mode and multimode port adapters available on the following routers:
•
•
•
•
Refer to the Cisco Product Catalog for hardware compatibility information and for specific model numbers of port adapters.
To enable half-duplex mode, use the no full-duplex or half-duplex commands.
Caution
router(config)# interface fastethernet 0router(config-if)# full-duplexPlease use duplex command to configure duplex moderouter(config-if)#router(config-if)# half-duplexPlease use duplex command to configure duplex modeSupport for This Command
Use the question mark command (?) to find out which port adapters support this command. If the interface does not support full-duplex, an informational message similar to the one shown below is displayed, and no changes are made to the interface. To determine if the interface supports full-duplex, use the show interfaces command. For example, the following message is displayed if the interface does not support full-duplex:
% interface does not support full-duplex.Use on FDDI
Full-duplex on the FDDI full-duplex port adapters allows an FDDI ring with exactly two stations to transform the ring into a full-duplex, point-to-point topology. To operate in full-duplex mode, there must be only two stations on the ring, the two stations must be capable of operating in full-duplex mode, and both stations must complete a full-duplex autoconfiguration protocol. There is no FDDI token in full-duplex mode. Refer to the Cisco Product Catalog for specific model numbers of port adapters.
Full-duplex autoconfiguration protocol allows an FDDI station to dynamically and automatically operate in either half-duplex (or ring) or full-duplex mode, and ensures that the stations fall back to ring mode when a configuration change occurs, such as a third station joining the ring.
After booting up, the FDDI stations begin operation in half-duplex mode. While the station performs the full-duplex autoconfiguration protocol, the station continues to provide data-link services to its users. Under normal conditions, the transition between half-duplex mode and full-duplex mode is transparent to the data-link users. The data-link services provided by full-duplex mode are functionally the same as the services provided by half-duplex mode.
If you change the full-duplex configuration (for example from disabled to enabled) on supported interfaces, the interface resets.
Examples
The following example configures full duplex mode on the Cisco 7000 series routers:
interface fastethernet 0/1 full-duplexThe following example specifies full-duplex binary synchronous communications (BSC) mode:
interface serial 0encapsulation bstunfull-duplexThe following example enables full-duplex mode on FDDI interface 0:
interface fddi 0/1/0full-duplexRelated Commands
half-duplex
interface fastethernet
interface fddi
interface serialhalf-duplex
Use the half-duplex interface configuration command to specify half-duplex mode on an SDLC interface or on the FDDI full-duplex, single-mode port adapter and FDDI full-duplex, multimode port adapter on the Cisco 7200 series, and Cisco 7500 series routers. Refer to the Cisco Product Catalog for specific model numbers of port adapters.
Use the no form of this command to reset the interface for full-duplex mode.
half-duplex
no half-duplexSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.1.
This command was modified in Cisco IOS Release 11.3 to include information on FDDI full-duplex, single-mode and multimode port adapters.
Note
SDLC Interfaces
The half-duplex command is used to configure an SDLC interface for half-duplex mode and is used on a variety of port adapters. Use the question mark command (?) to find out which port adapters support this command.
Caution
router(config)# interface fastethernet 0router(config-if)# full-duplexPlease use duplex command to configure duplex moderouter(config-if)#router(config-if)# half-duplexPlease use duplex command to configure duplex modeEnable Full-Duplex Mode
To enable full-duplex mode, use the no half-duplex or full-duplex commands.
Note
Example
The following example configures an SDLC interface for half-duplex mode:
encapsulation sdlc-primaryhalf-duplexRelated Commands
half-duplex controlled-carrier
Use the half-duplex controlled-carrier interface configuration command to place a low-speed serial interface in controlled-carrier mode, instead of constant-carrier mode. Use the no form of this command to return the interface to constant-carrier mode.
half-duplex controlled-carrier
no half-duplex controlled-carrierSyntax Description
This command has no arguments or keywords.
Default
Constant-carrier mode, where DCD is held constant and asserted by the DCE half-duplex interface.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.2.
This command applies only to low-speed serial DCE interfaces in half-duplex mode. Configure a serial interface for half-duplex mode by using the media-type half-duplex command. These interfaces are available on Cisco 2520 through 2523 routers.
Controlled-carrier operation means that the DCE interface has DCD deasserted in the quiescent state. When the interface has something to transmit, it asserts DCD, waits a user-configured amount of time, then starts the transmission. When the interface has finished transmitting, it waits a user-configured amount of time and then deasserts DCD.
Examples
The following examples place the interface in controlled-carrier mode and back into constant-carrier operation.
Changing to controlled-carrier mode from the default of constant-carrier operation:
interface serial 2half-duplex controlled-carrierChanging to constant-carrier operation from controlled-carrier mode:
interface serial 2no half-duplex controlled-carrierRelated Commands
half-duplex timer
physical-layerhalf-duplex timer
To tune half-duplex timers, use the half-duplex timer interface configuration command. Use the no form of this command, along with the appropriate keyword, to return to the default value for that parameter.
half-duplex timer {cts-delay value | cts-drop-timeout value | dcd-drop-delay value |
dcd-txstart-delay value | rts-drop-delay value | rts-timeout value | transmit-delay value}no half-duplex timer {cts-delay value | cts-drop-timeout value | dcd-drop-delay value |
dcd-txstart-delay value | rts-drop-delay value | rts-timeout value | transmit-delay value}You can configure more than one of these options, but each option must be specified as a separate command.
Syntax Description
Default
The default cts-delay value is 0 milliseconds.
The default cts-drop-timeout value is 250 milliseconds.
The default dcd-drop-delay value is 100 milliseconds.
The default dcd-txstart-delay value is 100 milliseconds.
The default rts-drop-delay value is 3 milliseconds.
The default rts-timeout value is 3 milliseconds.
The default transmit-delay value is 0 milliseconds.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
The half-duplex timer command is used to tune half-duplex timers. With these timer tuning commands you can adjust the timing of the half-duplex state machines to suit the particular needs of their half-duplex installation.
Note
Value Ranges
The range of values for the cts-delay and rts-timeout keywords are dependent on the serial interface hardware.
Example
The following example set the cts-delay timer to 10 ms and the transmit-delay timer to 50 milliseconds:
interface serial 2half-duplex timer cts-delay 10half-duplex timer transmit-delay 50Related Commands
half-duplex controlled-carrier
physical-layerhold-queue
To specify the hold-queue limit of an interface, use the hold-queue interface configuration command. Use the no form of this command with the appropriate keyword to restore the default values for an interface.
hold-queue length {in | out}
no hold-queue {in | out}Syntax Description
length
Integer that specifies the maximum number of packets in the queue.
in
Specifies the input queue.
out
Specifies the output queue.
Default
The default input hold-queue limit is 75 packets. The default output hold-queue limit is 40 packets. These limits prevent a malfunctioning interface from consuming an excessive amount of memory. There is no fixed upper limit to a queue size.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The input hold queue prevents a single interface from flooding the network server with too many input packets. Further input packets are discarded if the interface has too many input packets outstanding in the system.
If priority output queueing is being used, the length of the four output queues is set using the priority-list global configuration command. The hold-queue command cannot be used to set an output hold queue length in this situation.
For slow links, use a small output hold-queue limit. This approach prevents storing packets at a rate that exceeds the transmission capability of the link. For fast links, use a large output hold-queue limit. A fast link may be busy for a short time (and thus require the hold queue), but can empty the output hold queue quickly when capacity returns.
To display the current hold queue setting and the number of packets discarded because of hold queue overflows, use the EXEC command show interfaces.
Note
Example
The following example sets a small input queue on a slow serial line:
interface serial 0 hold-queue 30 inRelated Commands
show interfaces
hssi external-loop-request
Use the hssi external-loop-request interface configuration command to allow the router to support a CSU/DSU that uses the LC signal to request a loopback from the router. Use the no form of this command to disable the feature.
hssi external-loop-request
no hssi external-loop-requestSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
The HSA applique (on the HSSI) contains an LED that indicates the LA, LB, and LC signals transiting through the devices. The CSU/DSU uses the LC signal to request a loopback from the router. The CSU/DSU may want to do this so that its own network management diagnostics can independently check the integrity of the connection between the CSU/DSU and the router.
Use this command to enable a two-way, internal, and external loopback request on HSSI from the CSU/DSU.
Note
Example
The following example enables a CSU/DSU to use the LC signal to request a loopback from the router:
hssi external-loop-requesthssi internal-clock
To convert the HSSI interface into a clock master, use the hssi internal-clock interface configuration command. Use the no form of this command to disable the clock master mode.
hssi internal-clock
no hssi internal-clockSyntax Description
This command has no arguments or keywords.
Default
Disabled
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.0.
Use this command in conjunction with the HSSI null-modem cable to connect two Cisco routers together with HSSI. You must configure this command at both ends of the link, not just one.
Note
Example
The following example converts the HSSI interface into a 45 MHz clock master:
hssi internal-clock 45 MHzhub
To enable and configure a port on an Ethernet hub of a Cisco 2505 or Cisco 2507, use the hub global configuration command.
hub ethernet number port [end-port]
Syntax Description
Default
No hub ports are configured.
Command Mode
Global configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 10.3.
Examples
The following example enables port 1 on hub 0:
hub ethernet 0 1no shutdownThe following example enables ports 1 through 8 on hub 0:
hub ethernet 0 1 8no shutdownRelated Commands
shutdown
ignore-dcd
Use the ignore-dcd interface configuration command to configure the serial interface to monitor the DSR signal (instead of the DCD signal) as the line up/down indicator. Use the no form of this command to restore the default.
ignore-dcd
no ignore-dcdSyntax Description
This command has no arguments or keywords.
Default
The serial interface, operating in DTE mode, monitors the DCD signal as the line up/down indicator.
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.0.
This command applies to Quad Serial NIM interfaces on the Cisco 4000 series routers and Hitachi-based serial interfaces on the Cisco 2500 and 3000 series routers.
Serial Interfaces in DTE Mode
When the serial interface is operating in DTE mode, it monitors the Data Carrier Detect (DCD) signal as the line up/down indicator. By default, the attached DCE device sends the DCD signal. When the DTE interface detects the DCD signal, it changes the state of the interface to up.
SDLC Multidrop Environments
In some configurations, such as an SDLC multidrop environment, the DCE device sends the Data Set Ready (DSR) signal instead of the DCD signal, which prevents the interface from coming up. Use this command to tell the interface to monitor the DSR signal instead of the DCD signal as the line up/down indicator.
Example
The following example configures serial interface 0 to monitor the DSR signal as the line up/down indicator:
interface serial 0ignore-dcdignore-hw local-loopback
To disable the monitoring of the LL pin when in DCE mode, enable the ingnore-hw local-loopback interface configuration command. To return to the default, use the no form of this command.
ignore-hw local-loopback
no ignore-hw local-loopbackSyntax Description
This command has no arguments or keywords.
Default
Enable
Command Mode
Interface configuration
Usage Guidelines
This command first appeared in Cisco IOS Release 11.3.
Use this command if your system is experiencing spurious modem interrupts, which momentarily causes the interface to enter loopback mode. The end result of this behavior is flapping and the loss of SDLLC sessions.
Note
Example
The following example displays how to disable the monitoring of the LL pin when in DCE mode:
Router#conf termRouter(config)#interface serial 2
