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Checking the Configuration
PA-4T+ Synchronous Serial Port Adapter Installation and Configuration8-22
Following is an example of a successful ping command to a remote server with the address
10.10.10.10:
Router# ping 10.10.10.10 <Return>
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echoes to 10.10.10.10, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/15/64 ms
Router#
If the connection fails, verify that you have the correct IP address for the server and that the server
is active (powered on), and repeat the ping command.
The loopback test allows you to detect and isolateequipment malfunctions by testing the connection
between the PA-4T+ interface and a remote device such as modems or CSU/DSUs. The loopback
subcommand sends a series of packets out to and through the device (or cable), and back to the
PA-4T+ interface. If the packets complete the loop, the connection is good. If not, you can isolate a
fault to the remote device or interface cable in the path of the loopback test.
Note You must configure a clock rate on the port before performing a loopback test. However, if no
cable is attached to the port, the port is administratively up, and the port is in loopback mode, you
do not have to configure a clock rate on the port before performing a loopback test.
Depending on the mode of the port, issuing the loopback command checks the following path:
• When no interface cable is attached to the PA-4T+ interface, or if a DCE cable is attached to a
port that is configured as line protocol up, the loopback command tests the path between the
network processing engine and the interface port only (without leaving the network processing
engine and port adapter).
• When a DTE cable is attached to the port, the loopback command tests the path between the
network processing engine and the near (network processing engine) side of the DSU or modem
to test the PA-4T+ interface and interface cable.
For complete descriptions of interface subcommands and the configuration options available for
Cisco 7200 series routers, Cisco uBR7200 series, and Cisco 7100 series routers, and VIP2
interfaces, refer to the publications listed in the“Related Documentation” section on page vi.
Note The X.21interface definitiondoes not includea loopbackdefinition. On thePA-4T+, the X.21
DTE interface does not support the loopback function. Because of the internal clock signal present
on the PA-4T+ interfaces, loopback will function on an X.21 DCE interface.