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

1. Create a Loopback

• 1. Create a Physical Loopback for a Fiber-Optic Interface

Connect the transmit port to the receive port.

• 2. 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.

• 3. Configure a Local Loopback

[edit interfaces interface-name (fastether-options | gigether-options)]
set loopback
show
commit

2. Verify That the Fast Ethernet or Gigabit Ethernet Interface Is Up

show interfaces (fe-fpc/pic/port | ge-fpc/pic/port)

3. 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

4. Clear Fast Ethernet or Gigabit Ethernet Interface Statistics

clear interfaces statistics fe-fpc/pic/port | ge-fpc/pic/port

5. 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

6. Check for Fast Ethernet or Gigabit Ethernet Interface Error Statistics

show interfaces (fe-fpc/pic/port | ge-fpc/pic/port ) extensive

Perform Steps 2 through 8 from Diagnose a Suspected Hardware Problem with a Fast Ethernet or Gigabit Ethernet Interface.