A DSL subscriber says that his DSL modem is trained at the subscribed rates, 1024 kbps downstream and 256 kbps upstream, but he has no access to the internet. The internet service was working until today. The modem remains trained – it is not dropping train or frequently retraining. Manually retraining the modem does not correct the problem. The customer can ping from his PC to the Ethernet interface on the DSL modem, but not addresses “in the network”. Initial troubleshooting shows that the DSL modem can ping the subscriber’s PC, but no addresses in the network. What could cause this problem?

A.
A telephone is connected to the DSL line with no microfilter or splitter installed. The phone is “loading” the line and disrupting DSL service.

B.
The subscriber powered-down the DSL modem, and when it was powered-up it defaulted to G.Lite mode (G.992.2). The port in the DSLAM is full-rate DMT (G.992.1).

C.
The DSL port in the DSLAM was left in a “shutdown” state by mistake following DSLAM maintenance.

D.
There is a problem with the subscriber’s ATM PVC between the DSLAM and ATM switch. An incorrect VCI was assigned between the DSLAM and ATM switch shortly after midnight, during the service provider’s network rearrangements.