IBM SC30-3681-08 manual Orphan Circuits, For FR DTE to DTE connectivity is lost, An orphan

Using Frame Relay

end-to-end PVC connection is not established. Router B receives an inactive status for that PVC.

B

Router DLCI 19

B

Frame

Relay

Backbone

Router

D

	physical connection
	logical connection
		Router
		A
Figure 22. DLCIs in Frame Relay Network
When the LMI and SVCsare disabled, the FR interface is running on a serial line
and a DTE cable is being used, the FR protocol asserts the DTR and RTS modem
control signals. (The Control signal is asserted for X.21). The FR interface goes up
once the DSR, CTS, and DCD modem control signals are on. (When X.21 is used,
the FR interface goes up once the Indication modem control signal is on.) The FR
interface is down or in the testing state if either DSR, CTS, or DCD are off or, when
X.21 is used, the Indication signal is off. Therefore, you need to ensure that the
modem, modem eliminator, or DSU that is used drops one or more of these signals
when the physical connection to the FR switch or the other FR DTE (if con®gured
for FR DTE to DTE connectivity) is lost.
Orphan Circuits
An orphan permanent virtual circuit is any PVC that is not con®gured for your router
but is learned indirectly through the actions of the network management entity. For
example, Figure 23 on page 391 assumes that router B has a con®gured PVC to
router D, but none to router A. Router A con®gures a PVC to router B. Router B
would then learn about the PVC to router A from LMI messages and classify it as
an orphan.
Orphan PVCs are treated the same as con®gured circuits except that you may
enable or disable their use with the enable orphan-circuitand disable
orphan-circuit commands.
By disabling orphan circuits, you add a measure of security to your network by
preventing any unauthorized entry into your network from a non-con®gured circuit.

390MRS V3.2 Software User's Guide