Frame Relay Components - Page 4

By Cisco Press | Posted Jan 10, 2002
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This same concept applies to Frame Relay DLCIs; the DLCI assignment is locally significant. The distant-end of the VC is unaware of this number because it has its own local DLCI assignment to identify the distant-end node. This is illustrated in Figure 15-7.

Figure 15-7: Frame Relay Network with DLCI Assignment
Click image for larger view in a new window
(Click image for larger view in a new window)

In this example, for Los Angeles to send traffic to New York, the FRAD will map the network layer information, such as IP address, to the DLCI. In this case, the DLCI is 100. New York will see traffic arrive on DLCI 425 and will be able to identify within its Frame Relay mapping tables that this traffic has arrived from Los Angeles.

Table 15-3 provides a view of the Frame Relay network shown in Figure 15-7.

Table 15-3
Table 15-3: Frame Relay DLCI Table for Figure 15-7

Site A Site BA -> B DLCIB -> A DLCI
Los Angeles New York 100 425
Los Angeles Seattle 150 258
Seattle New York 685 367
Seattle Los Angeles 258 150
New York Seattle 367 685
New York Los Angeles 425 100


NOTE:   The show frame-relay map command can be used in Privileged Exec mode to view the mapping of network addressing to a DLCI.

NOTE:   To define the mapping between a destination protocol address and the DLCI used to connect to the destination address, use the frame-relay map interface configuration command. Use the no form of this command to delete the map entry.
frame-relay map protocol protocol-address dlci [broadcast] [ietf | cisco] 
[payload-compress {packet-by-packet | frf9 stac [hardware-options]}]
no frame-relay map protocol protocol-address

Table 15-4: frame-relay map Command Field Descriptions

Field Description
Protocol Supported protocol, bridging, or logical link control keywords: appletalk, decnet, dlsw, ip, ipx, llc2, rsrb, vines and xns.
protocol-address Destination protocol address.
Dlci DLCI number used to connect to the specified protocol address on the interface.
Broadcast (Optional) Forwards broadcasts to this address when multicast is not enabled (see the frame-relay multicast-dlci command for more information about multicasts). This keyword also simplifies the configuration of Open Shortest Path First (OSPF).
Ietf (Optional) Internet Engineering Task Force (IETF) form of Frame Relay encapsulation. Used when the router or access server is connected to another vendors equipment across a Frame Relay network.
Cisco (Optional) Cisco encapsulation method.
payload-compress packet-by-packet (Optional) Packet-by-packet payload compression using the Stacker method.
payload-compress frf9 stac (Optional) Enables FRF.9 compression using the Stacker method.
If the router contains a compression service adapter (CSA), compression is performed in the CSA hardware (hardware compression).

If the CSA is not available, compression is performed in the software installed on the VIP2 (distributed compression).

If the VIP2 is not available, compression is performed in the routers main processor (software compression).

hardware-options distributed (Optional) -- Specifies that compression is implemented in the software that is installed in a VIP2. If the VIP2 is not available, compression is performed in the routers main processor (software compression). This option applies only to the Cisco 7500 series.

software (Optional) -- Specifies that compression is implemented in the Cisco IOS software installed in the routers main processor.

csa csa_number (Optional) -- Specifies the CSA to use for a particular interface. This option applies only to Cisco 7200 series routers.

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