Each router connects to the Frame Relay switch through a channel service unit/data
service unit (CSU/DSU).
2. When Frame Relay is con?¬?gured on an interface, the router sends an LMI status
inquiry message to the Frame Relay switch. The message noti?¬?es the switch of the
router status and asks the switch for the connection status of the router VCs.
3. When the Frame Relay switch receives the request, it responds with an LMI status
message that includes the local DLCIs of the PVCs to the remote routers to which the
local router can send data.
4. For each active DLCI, each router sends an Inverse ARP packet to introduce itself.
Figure 8-27 illustrates the ?¬?rst four steps of this process.
Figure 8-27 Stages of Inverse ARP and LMI Operation
5. When a router receives an Inverse ARP message, it creates a map entry in its Frame Relay
map table that includes the local DLCI and the remote router network layer address.
Note that the router DLCI is the local DLCI, not the DLCI that the remote router is using.
Any of the three connection states can appear in the Frame Relay map table.
6. Every 60 seconds, routers send Inverse ARP messages on all active DLCIs.
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