Use Loopback Testing for T1 Interfaces

This chapter describes using loopback testing to isolate T1 interface problems. (See Table 9.)

Table 9: Checklist for Using Loopback Testing for T1 Interfaces

T1 Interface Loopback Testing Tasks	Command or Action
Diagnose a Suspected Hardware Problem with a T1 Interface
Create a Loopback
Create a Physical Loopback	Connect a T1 loopback plug.
Configure a Local Loopback	[edit interfaces interface-name t1-options] set loopback local show commit
Set Clocking to Internal	[edit interfaces interface-name] set clocking internal show commit
Verify That the T1 Interface Is Up	show interfaces t1-fpc/pic/port
Clear T1 Interface Statistics	clear interfaces statistics t1-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	show interfaces t1-fpc/pic/port show interfaces t1-fpc/pic/port terse
Ping the T1 Interface	ping interface t1-fpc/pic/port local-IP-address bypass-routing count 1000 rapid
Check for T1 Interface Error Statistics	show interfaces t1-fpc/pic/port extensive
Diagnose a Suspected Circuit Problem
Create a Loop from the Router to the Network	[edit interfaces interface-name t1-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 T1 Interface.