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ADSL2 and ADSL2+ Interfaces on NFX350 Devices

ADSL Interface Overview

Asymmetric digital subscriber line (ADSL) technology is part of the xDSL family of modem technologies that use existing twisted-pair telephone lines to transport high-bandwidth data. ADSL lines connect service provider networks and customer sites over the "last mile" of the network—the loop between the service provider and the customer site.

ADSL transmission is asymmetric because the downstream bandwidth is typically greater than the upstream bandwidth. The typical bandwidths of ADSL2 and ADSL2+ circuits are defined in Table 1.

Table 1: Standard Bandwidths of DSL Operating Modes

Operating Modes




1—1.5 Mbps

12—14 Mbps


1—1.5 Mbps

24—25 Mbps

ADSL2 and ADSL2+ support the following standards:

  • LLCSNAP bridged 802.1q

  • VC MUX bridged

Supported security devices with xDSL SFP can use PPP over Ethernet(PPPoE) to connect through ADSL lines only.

ADSL2 and ADSL2+

The ADSL2 and ADSL2+ standards were adopted by the ITU in July 2002. ADSL2 improves the data rate and reach performance, diagnostics, standby mode, and interoperability of ADSL modems.

ADSL2+ doubles the possible downstream data bandwidth, enabling rates of 20 Mbps on telephone lines shorter than 5000 feet (1.5 km).

ADSL2 uses seamless rate adaptation (SRA) to change the data rate of a connection during operation with no interruptions or bit errors. The ADSL2 transceiver detects changes in channel conditions—for example, the failure of another transceiver in a multicarrier link—and sends a message to the transmitter to initiate a data rate change. The message includes data transmission parameters such as the number of bits modulated and the power on each channel. When the transmitter receives the information, it transitions to the new transmission rate.

Example: Configuring ADSL SFP Interface on NFX350 Devices


This example uses the following hardware and software components:

  • NFX350 device running the Junos OS Release 19.4R1 version, which supports the reoptimized architecture.


In this example, you are configuring ADSL SFP interface on an NFX350 device with the following configurations:

  • Physical interface - ge-0/0/11

  • ADSL SFP options - vpi3, vci34, and encap llcsnap-bridged-802dot1q


Ensure that connectivity to the host is not lost during the configuration process.



Step-by-Step Procedure

To configure ADSL SFP interfaces on NFX350 devices:

  1. Connect to the host.

  2. Allocate hugepages:

    Reboot the device.

  3. Configure virtual interfaces:

  4. Create VLANs using VLAN IDs:

  5. Configure interfaces:

  6. Commit the configuration.