Compatible Systems 5.4 Manuale Utente
Appendices
293
Network/protocol addresses are associated with each PVC using one of two
methods: static mapping, or the Inverse Address Resolution Protocol (IARP).
methods: static mapping, or the Inverse Address Resolution Protocol (IARP).
IARP is outlined in RFC 1293. IARP allows dynamic mapping of protocol
addresses to a DLCI. It can be used for IP, IPX and AppleTalk. It is more flex-
ible and easier to configure than static configuration.
addresses to a DLCI. It can be used for IP, IPX and AppleTalk. It is more flex-
ible and easier to configure than static configuration.
IARP is used when a router discovers a new PVC with its corresponding
DLCI on a physical interface. The PVC is discovered by communicating with
the Frame Relay switch using the LMI protocol. This may be done when the
router is coming up or when a PVC has come back up after going down for
some reason.
DLCI on a physical interface. The PVC is discovered by communicating with
the Frame Relay switch using the LMI protocol. This may be done when the
router is coming up or when a PVC has come back up after going down for
some reason.
A Frame Relay Example
The following diagram shows three remote office 56K Frame Relay connec-
tions feeding one central office T1 connection. Note that the PVCs are shown
as virtual point-to-point links which run through the physical connections and
the Frame Relay cloud.
tions feeding one central office T1 connection. Note that the PVCs are shown
as virtual point-to-point links which run through the physical connections and
the Frame Relay cloud.
A Frame Relay Example
The DLCI numbers in the diagram are only locally significant. That is, DLCI
numbers can only be guaranteed to not be duplicated locally, and a DLCI at
one location has no significance at another location.
numbers can only be guaranteed to not be duplicated locally, and a DLCI at
one location has no significance at another location.
Frame Relay Cloud
T1 Connection
56K Connection
56K Connection
56K Connection
PVC A
PVC B
PVC C
DLCI #10
DLCI #11
DLCI #12
DLCI #72
DLCI #72
DLCI #10