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loopback
Configures a SONET/SDH interface to either loop back through the transmitter or through the receiver.
Syntax: [no] loopback {internal | line}
line
Sets the SONET interface to loop the incoming data stream back through the transmitter.
internal
Sets the SONET interface to loop the outgoing data stream back through the receiver.
Description: Local loopbacks are used to test that a POS port is functioning correctly.
NOTE Loopbacks are used on SONET interfaces to test whether the port is correctly functioning. Routing protocol loopback interfaces are used to disconnect routing from the operation of the underlying interface. See interface in the "Interface Commands" chapter for information about routing protocol loopback interfaces.
Use the loopback command with the line argument to set the interface to loop incoming packets out through the transmit fiber. This sends incoming traffic unchanged back to the sender.
Use the no loopback line command to disable an incoming loopback.
Use the loopback command with the internal argument to set the interface to loop outgoing packets back in through the receive fiber. This sends outgoing traffic unchanged back into the router.
Use the no loopback internal command to disable an outgoing loopback.
Factory Default: No loopback configured.
Command Mode: POS interface configuration.
Example: In the following example:
- The interface pos command defines a POS interface
- The loopback internal command sets the interface to loop outgoing packets back in through the receive fiber
- The show interface pos command (in Executive mode) displays the new setting in the SONET Loopback field:
router(config-if)#loopback internal
This command will take the port out of service.
Are you sure [yes|no]? yes
Port configured for loopback...
router(config-if)#end
router#show interfaces atm 1/6/1
ATM 1/6/1 interface status is administratively down
MTU 4470 bytes, BW 155.520004 Mbit/Sec
Payload BW: 150.335999 Mbit/Sec, Total BW: 155.520004 Mbit/Sec
Encapsulation ATM
Loopback: Equipment, Keepalive: Disabled, Scramble: Enabled
ILMI: Disabled, keepalive: 1, Status: DOWN
ILMI Connection Check Interval: 5, Number Of Retries: 4
VC: Max Number of VCs is 200, Current Number of VCs is 5
Signalling VC = (null), ILMI VC vpi/vci = 0/0
UNI Version: configured 4.0, negotiated 4.0, Link Side: User
VPI max bits: local 8, actual 8
VCI max bits: local 16, actual 16
Received:
0 bytes 0 cells
0 discards, 0 errors
Transmitted:
0 bytes, 0 cells
Medium Type SONET, Line Coding: NRZ, Line Type: Unknown
Sonet Loopback: Equipment, Sonet Clock Source: Line
Sonet/Path: SNMP Trap sonet link-status: enabled
Tx J0 Section Trace: "1"
Rx J0 Section Trace: "1"
Tx Path Trace: ROYS_POS/ATM 1/6/1/3
Rx Path Trace: <NULL>
router#
Related Commands: show interface pos
interface
show interface loopback
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Source
File Name: SONET.fm
HTML File Name: SONET4.html
Last Updated: 02/25/05 at 14:29:54