Using Loopback Commands; Oc12 Pos Statistics Counters - Cisco 7300-1OC12POS-MM Installation And Configuration Manual

OC12 POS Statistics Counters

Router#
If the connection fails, verify that you have the correct IP address for the destination and that the device
is active (powered on), and repeat the ping command.

Using loopback Commands

The loopback test allows you to troubleshoot, detect, and isolate equipment malfunctions by testing the
connection between the OC-12 interface and a remote device. The loop subcommand places an interface
in internal loopback (also called local loopback) or line loopback mode, which enables test packets that
are generated from the ping command to loop through a remote device or a cable. If the packets complete
the loop, the connection is good. If not, you can isolate a fault to the remote device or the cable in the
path of the loopback test.
Configuring an Interface for Internal Loopback
The default loopback setting is for no loopback. With internal (or local) loopback, packets from the
router are looped back in the framer. Outgoing data gets looped back to the receiver without actually
being transmitted. Internal loopback is useful for checking that the OC12 POS line card is working.
To configure an interface for internal loopback, enter the loop internal command:
Router(config)# interface pos 3/0
Router(config-if)# loop internal
To disable internal loopback, enter the no loop internal command.
Configuring an Interface for Line Loopback
The default loopback setting is for no loopback. With line loopback, the receive (RX) fiber is logically
connected to the transmit (TX) optical fiber cable so that packets from the remote router are looped back
to it. Incoming data gets looped around and retransmitted without actually being received. To configure
an interface for line loopback, enter the loop line command:
Router(config)# interface pos 3/0
Router(config-if)# loop line
To disable line loopback, enter the no loop line command.
OC12 POS Statistics Counters
The OC12 POS line card maintains counts of certain errors. Each error counter is 32 bits. Errors include
the following:
•
•
•
•
OC12 Packet Over SONET Line Card Installation and Configuration
4-12
CRC errors—Packet corrupted in reception
Giants received—Packet length too large (greater than MTU size)
Runts—Packet length too small (less than or equal to 4 bytes)
Ignores—No receive buffers available; receive buffers full
Chapter 4 Configuring the OC12 POS Line Card
OL-3437-01