This Technical Note describes troubleshooting tips for the Netopia S/A Router.

Problem:

This Technical Note focuses on troubleshooting techniques for a Leased Line Netopia Router using an external DSU, with an emphasis on North American T1 and Fractional T1 lines. Higher level datalink protocols like PPP, HDLC and Frame Relay are not referenced here but are the topic of another Technical Note.

Parameters:

Below is a list of hardware and firmware loads that this Technical Note is based upon:

Network Configuration:

None.

Background:

The Synchronous/Asynchronous (S/A) card available in North America and Internationally for the Netopia Router can connect to a T1 or Fractional T1, E1 or Fractional E1, or DDS line through an external DSU.

Leased Lines in North American are based upon a 64,000 bits/s (64 Kbps) channel, referred as a DS0 (Digital Signal Level Zero). Twenty four of these channels are grouped together to form a DS1, also referred to as a T1 (or T Carrier) line. Each channel can carry digitized voice or data.

Bits of data sent over a T1 line are sent in frames, and each T1 frame is twenty four time slots of eight bits apiece. Therefore twenty four timeslots multiplied by eight bits yields 192 bits in a T1 frame. Frames are sent at 8,000 times per second over a T1 line, for a payload data rate of 1,536,000 bits/s (1.536 Mbps).

There is an additional framing bit which is required to let end systems determine the start and stop of a frame. This produces a total of 193 bits per T1 frame, with a final T1 bit rate of 1,544,000 bits/s (1.533 Mbps). The user data rate will always be 1.536 Mbps, but only if clear channel is supported. If clear channel is not supported, each channel will be 56,000 bits/s for a total payload data rate of 1,344,000 bits/s (1.344 Mbps).

The Leased Line itself consists of four wires, or two pairs, terminated at an RJ-45 jack using pins 1,2,4,5.

Configuration:

The Netopia Router has six WAN LED's which give a status of the WAN connection and are helpful in troubleshooting connection problems. These LED's are described as follows:

The Netopia Router's WAN Ready LED will blink red when there is no connection to the Telephone Company or remote network. Possible causes of this could be as follows:

• Loose or defective V.35 or X.21 cable connection between the Netopia Routers S/A port and external DSU;
• An improperly configured or defective external DSU not providing signal to the Netopia Router;
• Bad or improperly pined out RJ-45 patch cable; Bad or improperly wired RJ-45 jack;
• Telephone company line problem.

A solid green WAN Ready LED indicates a physical connection between the local Netopia Router and DSU. Once this is done, the CH1 Link LED should come on indicating a connection to the remote network. If the CH1 Link LED does not come on, possible causes could be as follows:

• Incorrect data rate.
• An improperly configured or defective DSU.

All of these parameters are available and can be configured within the Netopia Router's console in the Serial Line Configuration screen. This information is provided by the Telephone Company or leased line provider. This screen looks like the following:

*************************************************************************

Serial Line Configuration

Data Rate (kbps)...           Auto

Invert Tx Clock:              No

Data Link Encapsulation...    Frame Relay



Enter Information supplied to you by your telephone company.
*************************************************************************

The Data Rate setting specifies the data rate of the leased line. There are twelve options, from Auto to 4096. Auto allows the Netopia Router to determine the line speed from the transmit clock generated by the DSU. If this is not available, the Data Rate can be manually configured.

If the CH1 Link LED is still not lit, the external DSU could be misconfigured. Verify the Leased Line settings with the Telephone Company or Leased Line provider and make sure the Line Encoding, Framing Mode, DS0 Channels, Buildout, Channel Data rate, and Clocking are set properly within the DSU.

Summary:

By following the troubleshooting steps in this Technical Note, this should eliminate connection or communication problems between the Netopia Router and remote equipment over a leased line. If the leased line still does not work properly, please contact the Telephone Company or leased line provider. They will be able to check the leased line configuration and perform loopback and bit-error tests to determine the source of any leased line problem.