IBM SC30-3681-08 manual Enable switched-virtual-circuit command, Orphan Circuit

Using Frame Relay

By enabling orphan circuits, you allow the router to forward packets over circuits you did not con®gure. Packets that would normally be dropped are now forwarded.

Frame

DLCI 19Relay

Backbone

Router

B

physical connection
logical connection	DLCI 18

Router

A

Figure 23. Orphan Circuit

Router

D

Orphan circuit (Configured in that direction only)

An orphan switched virtual circuit is an SVC that is not con®gured for your router

but is created when a call-in is received for it. This is similar to Figure 23. However,

Q.933 messages are used instead of LMI to generate the circuit and associate the

appropriate parameters with it. Orphan SVCs are treated the same as con®gured

SVCs except that you may enable or disable their use with the call-in option of the

enable switched-virtual-circuit command.

Con®guring PVC States to Affect the Frame Relay Interface State

You can control the operation of your Frame Relay interface by

1.Enabling the ªNo-PVCº feature or

2.Con®guring ªrequired PVCsº or

3.Con®guring ªrequired PVC groupsº.

By enabling the Frame Relay ªNo-PVCº feature, the Frame Relay interface becomes inactive when there are no active PVCs on the interface. If at least one PVC is active, the Frame Relay interface becomes active when a successful LMI exchange occurs between the router and the FR switch.

You can con®gure a PVC as a ªrequired PVCº. If a PVC is required but not in a group, the Frame Relay interface becomes inactive when the PVC becomes inactive. When the PVC becomes active, the interface is activated following a successful exchange of LMI frames between the router and the Frame Relay switch.

Chapter 30. Using Frame Relay Interfaces 391