Using Loopback Commands - Cisco 7304 Installation And Configuration Manual

Checking the Configuration

Using loopback Commands

With the loopback test, you can detect and isolate equipment malfunctions by testing the connection
between the 6E3 line card interface and a remote device such as a modem or a CSU/DSU. The loopback
command places an interface in loopback mode, which enables test packets that are generated from the
ping command to loop through a remote device or compact serial cable. If the packets complete the loop,
the connection is good. If not, you can isolate a fault to the remote device or compact serial cable in the
path of the loopback test.
Table 4-8
examples given are for interface 0 of a 6E3 line card in slot 2 of a Cisco 7304 router:
Table 4-8 Using loopback Commands
Command
loopback local
loopback network line
loopback network payload
loopback dte
Figure 4-1 on page 4-17
loopback.
Cisco 7304 6-Port Clear Channel E3 Line Card Installation and Configuration
4-16
provides examples of the loopback {dte | local | network {line | payload} command. The
Function
Sets the interface into local loopback mode.
Local loopback loops the router output data
back toward the router at the framer.
Sets the interface into network line loopback
mode. Network line loopback loops the data
back toward the network (before the framer).
Sets the interface into network payload
loopback mode. Network payload loopback
loops just the payload data back toward the
network at the E3 framer.
Sets the interface into loopback data terminal
equipment (DTE) mode. Loopback DTE
loops the router output data back toward the
router (after the LIU).
shows the data flow for three loopback configuration paths, including no
Chapter 4 Configuring the 6E3 Line Card
Example
Router(config)# interface serial 2/0
Router(config-if)# loopback local
Router(config)# interface serial 2/0
Router(config-if)# loopback network
line
Router(config)# interface serial 2/0
Router(config-if)# loopback network
payload
Router(config)# interface serial 2/0
Router(config-if)# loopback dte
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