246 CHAPTER 17: CONFIGURING FRAME RELAY
Virtual circuits can be divided into permanent virtual circuit and switching virtual
circuit, accordi ng to their diffe rent configuration method. Virtual circuits
configured manually are called Permanent virtual circuits (PVCs), and those created
by protocol negotiation are called switching virtual circuits (SVCs), which are
automatically created and deleted by Inverse ARP protocol. At present, the most
frequently used in Frame Relay is the permanent virtual circuit mode, i.e., manually
configured virtual circuit.
In the permanent virtual circuit mode, test the availability of the virtual circuit,
which is accomplished by the local management interface (LMI) protocol. The
3Com Router supports three LMI protocols: LMI complying with ITU-T Q.933
Appendix A, LMI complying with ANSI T1.617 Appendix D and non-standard LMI.
Their basic function is: DTE sends one Status Enquiry packet to query the virtual
circuit status at certain interval, after the DCE receives the packet, it will
immediately use the Status packet to inform DTE the status of all the virtual
circuits on current interface.
The status of Permanent virtual circuits (PVCs) on DTE is completely determined by
DCE. And the network determines the status of Permanent virtual circuits (PVCs)
of DCE. In case that the two network devices are directly connected, the
equipment administrator sets the virtual circuit status of DCE. In The 3Com Router,
the quantity and status of the virtual circuits are set at the time when address
mapping is set (with the fr map command). They can also be configured with the
Frame Relay local virtual circuit configuration command (fr dlci command).
Configure Frame Relay Frame Relay configuration includes:
■Configure the Link Layer Protocol of the Interface to Frame Relay
■Configure Frame Relay Terminal Type
■Configure Frame Relay LMI Type
■Configure the Related Parameters of Frame Relay LMI Protocol
■Configure Frame Relay Address Mapping
■Configure Frame Relay Local Virtual Circuit Number
■Configure Frame Relay Sub-Interface
■Configure Frame Relay PVC Switching
■Configure Multilink Frame Relay (FRF.16)
■Configure Frame Relay Payload Compression (FRF.9)
■Enable/Disable TCP/IP Header Compression on Interfaces
■Configure Frame Relay Fragment(FRF.12)
1Configure the Link Layer Protocol of the Interface to Frame Relay
Perform the following task in the interface view.
Tabl e 274 Configure the link layer protocol of interface to Frame Relay
By default, the interface's link layer protocol is PPP.
Operation Command
Configure the link layer protocol of interface to Frame
Relay link-protocol fr [ ietf |
nonstandard ]