I was looking at the config of a router with an E1 that has some latency issues and noticed the loopback command was configured under it's serial interface
CrumpOT-RTR#sh run int s 0/0/0:0
Current configuration : 241 bytes
description CircuitID ATNT-T4257
no ip address
ip nbar protocol-discovery
ip flow ingress
ip flow egress
encapsulation frame-relay IETF
service-policy output WAN-EDGE-CA&CM
hold-queue 50 out
Is there any reason the loopback command would be there except for bert testing during a loopback?
As far as i know Loopback command is required to check the link, i feel somebody might have tried giving soft loop and checked the same.
Might be done with the help of your Telco. Just to check the quality and reliability of the link.