Troubleshooting

If the light does not appear at that point, please turn the power off and then on again. If the LED still does not appear lighted, please call your service representative.

During normal operation the ALARM light will flash RED one time after the unit is powered. If the LED still flashes RED or lights RED and stays lighted, please call your service representative.

Note With the POWER light "On", the WAN LNK light may appear "Off" under certain circumstances, even though the Cisco 676 is operating correctly. This condition can occur, for instance, if there is no data traffic across the WAN LNK for a period of time.

During subsequent requests for data across the link, the WAN LNK light should start to blink, indicating that the ADSL connection sequence has started.

4.2 Web Interface Password Lengths

Web interface passwords can be from 1 to 7 characters in length. The web interface requires that you set a password. Refer to "Setting Passwords" section.

4.3 Web Browser Compatibility

Internet Explorer 2.0 from Microsoft is incompatible to use as a browser on the Cisco 676. Therefore, Netscape 3.01 or higher or Internet Explorer 3.01 or higher are recommended for use as browsers for the Cisco Web Management Interface.

4.4 Serial Buffer Overflow

When using the serial port as your terminal connection, large amounts of serial data may overflow the serial buffer. This results in ASCII garbage appearing to the screen but does not affect performance or operation in any way. To avoid this issue, use Telnet to manage the Cisco 676 .

4.5 Radius Password and User Name Lengths

RADIUS passwords must be less than or equal to 16 characters in length. RADIUS user names may be up to 255 characters in length. Refer to "RADIUS Client" section.

4.6 Computers Running Linux Without term/termcap

Computers running Linux without the "term"/"termcap" database installed will have trouble connecting to Cisco equipment. The message "BAD ADDRESS" is sometimes displayed as an error message. The user can install the "term"/"termcap" database from his/her Linux install disks/CD.

4.7 Clearing PC Cache With ARP

If you update IP addresses on many Cisco 676s in rapid succession using a Windows PC, the PCs ARP cache may not clear right away. This causes communications problems with the subsequent Cisco 676s in the line. To clear the PC cache, use the following command at the MS-DOS prompt on your PC:

c:\> arp -d 192.168.0.100

This deletes the MAC address and causes IP to ARP again at IP address 192.168.0.100. The ARP utility comes with Windows 95, 98 and NT, so if you don't have it in your current installation, you can install it from your original Windows install media.

4.8 RIP and Idle Timeouts

On a busy network with many RIP broadcasts and requests, RIP traffic alone can cause the Cisco 676 to remain sufficiently active to not trigger the idle timeout. It is recommended that RIP be disabled if Cisco 676 idle timeouts are used.

4.9 ADSL Parameters for `set interface'

The set interface wan0 command supports:

stay

Sets stay-trained mode. ADSL line will not retrain.

stay	Sets stay-trained mode. ADSL line will not retrain.

4.10 BERT Testing

This section describes BERT tests using a Cisco 6100, Cisco 676, and an optional HP Broadband test set.

4.10.1 HP Test Set Configuration

All tests are based on the single cell version of S-PRBS9. This is the only PRBS pattern that is supported by the HP for generating multiple channels of cell load. All cells will have the same data, therefore it is necessary to have a cell sequence number to verify cell loss. This is done using AAL-1.

Cells are generated by the HP and terminated by the Cisco 676 in the downstream direction, and vice versa for the upstream direction. The HP can only check BERT data on one channel at a time. It is therefore necessary to manually walk through every channel to verify data integrity. The BERT test can be performed without the HP test set if the Cisco 6100 NIU is physically looped back at the OC3 port.

4.10.2 Transmitting BERT Data

The following are the procedures for transmitting BERT data. Note that all pertinent tests will be initiated from the Optical Line Interface Card, and not a Cell Processor.

Configure the load generator (truck icon) to send S-PRBS9 data to each Cisco 676 on VPI X / VCI X. Starting with channel 2 on the load generator, set up a connection using VPI 1 / VCI 32. Continue with channel 3 as VPI 1 / VCI 33 and so on until the number of channels that need to be tested are accounted for.
Set the contents of each cell to S-PRBS9 with AAL-1 enabled. All channels can be done at once by highlighting all of the channels and then setting the contents. AAL-1 provides sequence numbers to determine if cells are being dropped.
Set the bandwidth to the desired downstream rate. Again, all channels can be highlighted and changed simultaneously. This rate should be slightly lower than the trained rate (e.g. 1.4M).
Configure the Cisco 6100, using ViewRunner, to set up connections from the NIs OC3 to the Cisco 676. Use the same connection parameters (VPI/VCI) that were used to configure the load generator.
Verify that no other cell generation sources are active on the HP and that the laser is turned on.
Compile the load generator and data will start flowing to the NI, through the Cisco 6100 and out to the Cisco 676. Every time a parameter is changed in the load generator it is necessary to compile for the change to take effect.
The Cisco 676 should now be receiving BERT data.

4.10.3 Receiving BERT Data

Once the Cisco 676 has been BERT-enabled, it will send S-PRBS9 BERT data towards the Cisco 6100. The HP can verify the BERT data once channel at a time. The following are the procedures for receiving BERT data. Note that the ViewRunner must be used to set up all of the connections to the HP (see above).

Select the receive filter from the Optical Line Interface Card and not the Cell Processor Card. This is the net/strainer icon.
Specify the VPI and VCI that needs to be checked. The receive filter mode should be Virtual Channel.
Select S-PRBS9 and AAL-1. Now, only the specified cells will make it to the statistics counters.
Select the statistics icon (ones and zeros). From there select View and then ATM Statistics.
Select Selected Cell Count, Bandwidth, Cell Loss, etc.
Apply
Select measurements and start the counters.

This will give you the statistics for the cell that is currently selected in the receive filter. Repeat the above procedure to check other channels. The Cell Protocol Processors can be used to view incoming cells if desired.

4.11 Cisco 676 Configuration

See the following procedures for configuring the Cisco 676:

Login to the Cisco 676 via Ethernet or serial port
Give access to the BERT commands:
cbos> enable debug commands <Enter>
Keep the Cisco 676 from trying to re-train even though it does not acknowledge a FireRunner on the far end:
cbos# ifconfig wan0 stay <Enter>
Initiate the BERT test:
cbos# debug bert on <Enter>
Set the header bits of the outgoing cells and qualify the incoming cells.
Then do: cbos# debug bert header 00100010 <Enter>

: Note that these are the four bytes of header not including the calculated HEC byte. See the table below for a description of the bit fields.
: Example: VPI=1, VCI=1 (GFC=0, PTI=0, CLP=0) across the ADSL loop (see command line above).

Table 4-1: BERT Header Bit Map

7 6 5 4 3 2 1 0

GFC

VPI

VPI

VCI

VCI

VCI

VCI

PTI

CLP

Display a count of the BERT errors and cell loss since the previous query:
cbos# debug bert count <Enter>


: Note that the top two LEDs on the Cisco 676 take on a new meaning during the BERT tests; as described below.

BERT SYNC LED---This is the top LED and is illuminated once the Cisco 676 detects a valid BERT pattern.
BERT ERROR LED---This is the second LED from the top and is toggled whenever the Cisco 676 detects a BERT error.

During a successful BERT test, the top LED will be illuminated, and the second LED will be solid (either off or on, but not blinking).

4.12 Frequently Asked Questions (FAQ)on the WAN LNK LED

The list in this section describes all known conditions indicated by the WAN LNK LED.

1. If the WAN LNK LED blinks continuously and never stays solid on, the 676 never trains to a system such as the Cisco 6100:

The ADSL line is not connected to the 676.
The subscriber is locked on the 6100.
The subscriber's LIM port is locked on the 6100.
The subscriber's LIM port is not associated to an ATU-C pool.
There are no available ATU-C's for the 676 to train up to.
The ADSL circuit is physically too long.
There is excessive noise on the ADSL circuit.

2. If the 676 trains up and the WAN LNK LED turns off after approximately 1:45 (105 seconds) when the 676 is in routing mode, this means that the 676 is not getting his PPP requests answered by the router on the service provider's network, such as the Cisco 7200. 105 seconds is the time it takes for three PPP requests to be sent from the 676, and if they are not answered by the Cisco 7200, the 676 stops sending them and the WAN LNK LED turns off. There are a number of possibilities why this would happen:

The VPI/VCI provisioning is not correct in the ATM cloud. This could signify that the Cisco 7200 or the ATM switch along the path does not have the correct provisioning.
The VPI/VCI mapping in the Cisco 7200 or the 676 is not configured properly.
ATM Cell scrambling is enabled on one end of the link but not the other. 'show running' will display an entry with "ATM WAN Cell Scrambling = disabled" if cell scrambling is disabled. No enty implies the default behavior of ATM cell scrambling is enabled.
The Cisco 7200 is powered off.
The 676 is configured for routing mode, but the Cisco 7200 (or other router at the service provider's network terminating 676 traffic) is configured for bridging.

3. If the 676 trains up and the WAN LNK LED turns off, this is a sign of no ATM cell delineation.Verify that you have the ATM link terminated at the central office end. Without ATM cell delineation , the router will attempt to retrain the line in 1-10 seconds.

4. If the 676 (676 only) trains up and then immediately drops the connection, the near-end DMT firmware may not be compatible with the far end DMT firmware . For example an ITU G.Lite modem may not train to an ANSI Issue 1 central office. To see the DMT firmware version installed on your modem use the show version command.

5. If the WAN LNK LED turns off after the 676 has successfully been transferring data end-to-end for some time, this means that the 676 or the Cisco 7200 might have a timeout set. There are 2 timeouts that could affect the WAN LNK LED:

IDLE timeout: This timeout can be set on the 676 or the Cisco 7200. If the IDLE timeout is set to some value, then the 676 WAN LNK LED will turn off if the 676 becomes idle for that specified period of time. The show timeout command will display the current timeout status and settings.
SESSION timeout: This timeout can be set on the 676 or the Cisco 7200. If the SESSION timeout is set to some value, then the 676 WAN LNK LED will turn off after that certain period of set time no matter if it idle or not. The show timeout command will display the current timeout status and settings.

6. If the WAN LNK LED goes solid for approximately four seconds and then turns off, this primarily points to a RADIUS problem. After the 676 trains and the Cisco 7200 that is being used to authenticate its PPP session is using RADIUS, then this could point to a failed RADIUS authentication. Possible reasons for a failed RADIUS authentication:

The Cisco 7200 has the wrong IP address for the RADIUS server.
The username and password on the 676 do not match to the username and password running on the RADIUS server's user list
The RADIUS server is not running.

: Disabling RADIUS on the Cisco 7200 would be a simple test to see if it is a RADIUS problem. Note that RADIUS is an application only available in routing mode.

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