Cisco 6000 Series IP DSL Switches

This document provides answers to some of the most frequently asked questions about the Cisco 6260 Digital Subscriber Line Access Muliplexer (DSLAM).

A. The Cisco 6260 with an NI2 module runs Cisco IOS Release 12.1.2-DA or later.

A. The Cisco 6260 might not recognize an ATUC-1-4DMT if you do not have the "boot system flash" statement in the configuration. Even if you have the image file stored in the flash, the NI2 might boot up with the boot image and not recognize the ATUC-1-4DMT cards.

Also, note that the config-register value is 0x2 when NI2 is shipped. This must be changed to 0x2102 in order to prevent a bootup problem.

A. Thirty 4-port standards compliant discrete multitone (DMT) line cards (120 modems) per shelf can be put in the chassis.

A. A DSL profile is a named list of configuration parameters which is attached to the subscribers. The parameters for Operating Mode, Training Mode, Bit Rate, SNR Margin, forward error correction (FEC) Bytes, Symbols per codeword, Interleaved Delay, Trellis Coding, Overhead Framing, Bit Swapping, Power Boost, and Bit Rate Alarm Threshold can be changed. When a parameter in a profile is changed, the value of that parameter on all ports using that profile is also changed.

A. The alarm command enables alarming on near-end conditions – loss of signal (LOS), loss of frame (LOF), or loss of cell delineation (LOCD), modem port failure or a data rate at or below the minimum bit rate.

A. The standard training mode takes about 30 seconds to train. The quick mode allows faster training but with less control over parameters.

A. A higher SNR margin provides more protection against data corruption but it lowers the data rate with which to be trained up.

A. The dmt bitrate <options> command configures the upstream and downstream bit rate parameters for the interleaved data path. The minimum bit rate setting is only pertinent to alarming. A minor alarm is raised when the data rates are not above the configured minimum bit rate.

A. Interleaving Delay helps to protect against impulse noise and clipping, but it adds delay which might not be tolerable for some delay-sensitive applications.

A. ATM0/0 is the interface to the switching fabric for terminating VC connections. It provides connections to the DSLAM CPU for control channels for Interim Local Management Interface (ILMI), signaling, Private Network-Network Interface (PNNI) and network management. Also, it configures the virtual path identifier (VPI) to be 0 for the CPU portion of a PVC that is not a tunnel. For the virtual channel identifier (VCI), select a VCI value greater than 300.

A. The 0/1 interface is for the trunk that connects to the network, either directly or through a subtended port in another DSLAM. The 0/2 interface is the subtended interface that connect to a second DSLAM. Only one subtended interface is available for OC3 configuration, while there is a second subtended interface, 0/3, for DS3 configuration.