Checklist for Using Loopback Testing for Fast Ethernet and Gigabit Ethernet Interfaces

To use loopback testing to isolate Fast Ethernet and Gigabit Ethernet interface problems.

Table 42 provides links and commands for using loopback testing for Fast Ethernet and Gigabit Ethernet interfaces.

Table 42: Checklist for Using Loopback Testing for Fast Ethernet and Gigabit Ethernet Interfaces

Tasks	Command or Action
Diagnose a Suspected Hardware Problem with a Fast Ethernet or Gigabit Ethernet Interface
Create a Loopback
Create a Physical Loopback for a Fiber-Optic Interface	Connect the transmit port to the receive port.
Create a Loopback Plug for an RJ-45 Ethernet Interface	Cross pin 1 (TX+) and pin 3 (RX+) together, and pin 2 (TX-) and pin 6 (RX-) together.
Configure a Local Loopback	[edit interfaces interface-name (fastether-options \| gigether-options)] set loopback show commit
Verify That the Fast Ethernet or Gigabit Ethernet Interface Is Up	show interfaces (fe-fpc/pic/port \| ge-fpc/pic/port)
Configure a Static Address Resolution Protocol Table Entry	show interfaces ge-fpc/pic/port [edit interfaces interface-name unit logical-unit-number family inet address address] set arp ip-address mac mac-address show commit run show arp no-resolve
Clear Fast Ethernet or Gigabit Ethernet Interface Statistics	clear interfaces statistics fe-fpc/pic/port \| ge-fpc/pic/port
Ping the Fast Ethernet or Gigabit Ethernet Interface	ping remote-IP-address bypass-routing interface (fe-fpc/pic/port \| ge-fpc/pic/port count 100 rapid
Check for Fast Ethernet or Gigabit Ethernet Interface Error Statistics	show interfaces (fe-fpc/pic/port \| ge-fpc/pic/port ) extensive
Diagnose a Suspected Circuit Problem	Perform Steps 2 through 8 from Diagnose a Suspected Hardware Problem with a Fast Ethernet or Gigabit Ethernet Interface.