Cisco Cisco IOS Software Release 12.3(4)T

SSG must be enabled on the router. 

You cannot use this command on an individual subinterface that is part of a permanent virtual circuit 
(PVC) range because all members of a range must have the same direction. You can use the command 
on the entire range only.

An interface that does not exist will not be created as a result of the ssg direction command.

Before you can change a direction from uplink to downlink, or the opposite, you must use the no ssg 
direction command to clear the direction. If you do not, you will receive an error message similar to the 
following:

Changing direction from Downlink to Uplink is denied for interface interface

Please use ‘no ssg direction downlink’ to clear the previous bind direction 

Before you configure the ssg direction command, you should understand the following concepts:

SSG is a switching solution for service providers who offer intranet, extranet, and Internet connections 
to subscribers using broadband access technology such as xDSL, cable modems, or wireless to allow 
simultaneous access to network services. It is a combined hardware and software solution that helps 
service providers provide differentiated kinds of services to users connecting through different mediums. 
SSG also offers user authentication and accounting features. 

SSG implements Layer 3 service selection through selective routing of IP packets to destination 
networks on a per-subscriber basis. SSG introduces the idea of interface direction (uplink/downlink) and 
uses this direction to help determine the forwarding path of an incoming packet. An uplink interface is 
an interface to services; a downlink interface is an interface to subscribers. You can set the direction by 
using the ssg direction command.