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Checking the Configuration
Table 4-8
Using loopback Commands (continued)
Command
loopback network payload
1
loopback remote
loopback dte
1. Remote loopback mode works with C-bit framing only. The other loopback modes listed above work with C-bit and M23 framing. Refer to the
"Specifying T3 Framing" section on page 4-9
Figure 4-1
Figure 4-1
LIU
LIU
Remote
host
Clear Channel 6-Port T3 (DS3) Line Card Installation and Configuration
4-16
Function
Sets the interface into network payload
loopback mode. Network payload
loopback loops just the payload data back
toward the network at the T3 framer.
Sets the interface into remote loopback
mode. Remote loopback loops the data
back toward the network (before the
framer at the remote T3 device).
Sets the interface into loopback data
terminal equipment (DTE). Loopback
DTE loops the router output data back
toward the router (after the LIU).
for information on configuring C-bit framing.
shows the data flow for three loopback configuration paths, including no loopback.
DS3 Loopback Paths
Tx DS3 framer
Rx DS3 framer
QJET
No loopbacks
Tx DS3 framer
Rx DS3 framer
QJET
Line loopback
Cable
Tx DS3 framer
LIU
Rx DS3 framer
Remote loopback
Example
Router(config)# interface serial 2/0
Router(config-if)# loopback network
payload
Router(config)# interface serial 2/0
Router(config-if)# loopback remote
Router(config)# interface serial 2/0
Router(config-if)# loopback dte
Tx/Rx
LIU
HDLC
Diagnostic or local loopback
Tx/Rx
LIU
HDLC
LIU
QJET
Chapter 4
Configuring the 6T3 Line Card
Tx DS3 framer
Tx/Rx
HDLC
Rx DS3 framer
QJET
Tx DS3 framer
Tx/Rx
HDLC
Rx DS3 framer
QJET
Payload loopback
Tx DS3 framer
Tx/Rx
HDLC
Rx DS3 framer
QJET
DTE loopback
OL-3449-02
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