ADTRAN 1000R Series - Manual (Page 202)

Command Reference Guide Enable Mode Command Set
61200510L1-35E Copyright © 2005 ADTRAN 202
Technology Review
A network loopback loops data toward the network (away from the unit). A customer loopback loops data
toward the router. The router does not instigate customer-side loopbacks, only network loopbacks (remote
or local). The reason for this is that the customer interface is internal to the router. There is little use for
looping back router data on itself.
A transparent loopback is one in which the unit loops back one side (i.e., network) and also allows the
same incoming data to be passed through to the customer side. A non-transparent loopback is one which
loops back one side of the interface (network) but sends idle codes to the other side (customer). The AOS
defaults to non-transparent loopbacks. The reason for this is that sending test patterns into the IP stack
could cause unpredictable behavior. However, it is still possible for the network to send a transparent
loopback request. Such requests will be accepted.