Use Loopback Testing for T3 Interfaces

This chapter describes using loopback testing to isolate T3 interface problems. (See Table 15.)

Table 15: Checklist for Using Loopback Testing for T3 Interfaces

T3 Interface Loopback Testing Tasks	Command or Action
Diagnose a Suspected Hardware Problem with a T3 Interface
Create a Loopback
Create a Physical Loopback	Connect the transmit port to the receive port.
Configure a Local Loopback	`[edit interfaces` `interface-namet3-options] set loopback local show commit`
Set Clocking to Internal	`[edit interfaces` `interface-name] set clocking internal show commit`
Verify That the T3 Interface Is Up	`show interfaces t3-fpc/pic/port`
Clear T3 Interface Statistics	`clear interfaces statistics t3-fpc/pic/port`
Force the Link Layer To Stay Up
Configure Encapsulation to Cisco-HDLC	`[edit interfaces` `interface-name] set encapsulation cisco-hdlc show commit`
Configure No-Keepalives	`[edit interfaces` `interface-name] set no-keepalives show commit`
Verify the Status of the Logical Interface	s`how interfaces` `t3-fpc/pic/portshow interfaces` `t3-fpc/pic/port` `terse`
Ping the T3 Interface	`ping interface t3-fpc/pic/port local-IP-address` `bypass-routing count 1000 rapid`
Check for T3 Interface Error Statistics	`show interfaces t3-fpc/pic/port` `extensive`
Diagnose a Suspected Circuit Problem
Create a Loop from the Router to the Network	`[edit interfaces` `interface-namet3-options] set loopback remote show`commit
Create a Loop to the Router from Various Points in the Network	Perform Steps 2 through 8 from Diagnose a Suspected Hardware Problem with a T3 Interface.