官网都有!

SDH口:

http://www.juniper.net/techpubs/en_US/junos14.2/topics/topic-map/sonet-interfaces-loopback-testing.html


FE/GE/XE口:

http://www.juniper.net/techpubs/en_US/junos14.2/topics/topic-map/ethernet-fast-and-gigabit-loopback-testing.html


T3口:

http://www.juniper.net/techpubs/en_US/junos14.2/topics/topic-map/t3-interfaces-loopback-testing.html


T1口:


http://www.juniper.net/techpubs/en_US/junos14.2/topics/topic-map/t1-interfaces-loopack-testing.html


ATM口:

http://www.juniper.net/techpubs/en_US/junos14.2/topics/topic-map/atm-interface-loopback-testing-use.html