
13-1
Using Frame Relay 13Frame Relay is a method of encapsulating network information that allows for fast  
delivery and high line utilization. PortMaster routers support Frame Relay over 
synchronous ports.
This chapter uses an example to demonstrate how to configure the PortMaster to 
connect to a synchronous line using Frame Relay. This chapter also explains how to 
configure Frame Relay subinterfaces
The following topics are discussed:
• “Overview of  Frame Relay” on page 13-1
• “Frame Relay Config uration on the PortMaster” on page 13-4
• “Configuration Steps for a Frame Relay Connection” on page 13-7
• “Troubleshooting a Frame Relay Configura tion” on page 13-11
• “Frame Relay Subinterfaces” on page 13-12
See the PortMaster Command Line Reference for more detailed command descriptions and 
instructions.
Overview of Frame Relay
Synchronous ports on PortMaster products can be configured to support Frame Relay 
connections. As opposed to a dedicated or leased line, a Frame Relay connection can be 
thought of as a virtual switch.
Frame Relay is a switched digital service that supports multiple virtual circuits, 
simultaneously connected to a site by a single physical circuit. Each site requires only 
one physical circuit into the Frame Relay network—usually referred to as a cloud—but 
can have several virtual circuits to reach other sites attached to the cloud.