cisco ccna implementing and administering cisco solutions

cisco ccna implementing and administering cisco solutions.To exchange LMI information between a DTE and a DCE, a VC must be used.To let the DTE and DCE know that a Frame Relay frame contains LMI information, a reserved VC is used to share the LMI information. The LMI type determines what DLCI address is used to exchange this information. Table 25.2 lists the DLCI addresses assigned to the 3 types of LMIs. DLCI is discussed in more depth in the next subsection.Keeping in mind the DLCI numbers listed in Table 25.2 O25.2.2DLCIEach VC has a unique local address, the DLCI, which means that the DLCI number of the VC may be different in each segment of the WAN. The carrier switch is responsible for converting the DLCI number used by one segment to the DLCI number used by the next segment.DLCI ExampleFigure 25.5 shows an example of DLCI usage with three routers and three carrier switches. Router A has a PVC to Router B, and a PVC to Router C. Here is a more in-depth look at the PVC between Router A and Router B. o This PVC spans three physical links from Router A.. Router A-Switch 1 (DLCI 200) . Switch 1-Switch 2(DLCI 200) .. Switch 2-Router B ( DLCI 201)Note that the DLCI is only locally meaningful: it only needs to be unique within each segment, and must not be unique throughout the Frame Relay network. This is similar to MAC addresses in Ethernet (see Chapter 9 for an example of this). Thus, the DLCI number can be different in different segments, and the operator switch is responsible for modifying the DLCI in the frame header to the DLCI value in the next segment. Figure25.5 shows this, where two DTE segments use different DLCI values (200 and 201, respectively), but refer to the same PVC.Also, elsewhere in the network, DLCI numbers 200 and 201 are used.o What is important is that the same segment uses the same DLCI number.For example, Router A has two PVCs going to different destinations,on the Router A -Switch 1 connection, the address values of these PVCs must be unique (200 and 201, respectively), but these values can be different in each network segment going to the destination.