Local Significance Approach to DLCI Assignment
Earlier chapters discussed the concept of DLCI local significance. In the context of local significance on a Frame Relay network, the end devices at two different ends of a connection can use a different DLCI to refer to that same connection. This section discusses setting up a Frame Relay DLCI addressing scheme using the local significance approach to DLCI assignment. Later in the section, an alternate addressing scheme using the global significance approach is examined. Global significance of DLCI is part of the LMI enhancements to Frame Relay.
Figure 4-6 shows a hub-and-spoke Frame Relay network with five nodes using a DLCI scheme that conforms to the concept of local significance.
The configuration files of the Frame Relay switch for the network depicted in Figure 4-6 with the local significance addressing approach are shown in Example 4-28.
Figure 4-6 Local Significance Addressing
Example 4-28 Configuration Files for Frame Relay Switch Using Local Significance Addressing
SW#show running-config <output omitted> hostname SW ! no ip routing ! frame-relay switching ! interface Serial1/0 ! Connection to Router Spoke A no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 201 interface Serial4/3 102 ! interface Serial1/1 ! Connection to Router Spoke B no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 301 interface Serial4/3 103 ! interface Serial1/7 ! Connection to Router Spoke D no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 501 interface Serial4/3 105 ! interface Serial4/1 ! Connection to Router Spoke C no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 401 interface Serial4/3 104 ! interface Serial4/3 ! Connection to the Hub Router no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 102 interface Serial1/0 201 frame-relay route 103 interface Serial1/1 301 frame-relay route 104 interface Serial4/1 401 frame-relay route 105 interface Serial1/7 501 SW#show frame-relay route Input Intf Input Dlci Output Intf Output Dlci Status Serial1/0 201 Serial4/3 102 active Serial1/1 301 Serial4/3 103 active Serial1/7 501 Serial4/3 105 active Serial4/1 401 Serial4/3 104 active Serial4/3 102 Serial1/0 201 active Serial4/3 103 Serial1/1 301 active Serial4/3 104 Serial4/1 401 active Serial4/3 105 Serial1/7 501 active SW#
On a Frame Relay network using the global addressing approach, a unique DLCI address is assigned to each Frame Relay DTE device, including routers. The global addressing scheme allows Frame Relay devices to be uniquely identified by their assigned DLCIs. However, similar to the constraints of IP addressing, an assigned DLCI value cannot be reused in any other parts of the same Frame Relay network. In addition to this constraint, the number of Frame Relay devices that can be supported by global addressing is limited. Because global addressing requires the DLCI values to be unique, the maximum number of Frame Relay devices allowed is 992 (1024 possible DLCI values 32 reserved DLCI addresses). Figure 4-7 presents an example of a Frame Relay network utilizing the global addressing scheme.
Figure 4-7 Global Significance Addressing
The configuration files of the Frame Relay switch for the network depicted in Figure 4-7 with the global significance addressing approach are shown in Example 4-29.
Example 4-29 Configuration Files for Frame Relay Switch Using Global Significance Addressing
SW#show running-config <output omitted> hostname SW ! no ip routing ! frame-relay switching ! interface Serial1/0 ! Connection to Router Spoke A no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 101 interface Serial4/3 201 ! interface Serial1/1 ! Connection to Router Spoke B no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 101 interface Serial4/3 301 ! interface Serial1/7 ! Connection to Router Spoke D no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 101 interface Serial4/3 501 ! interface Serial4/1 ! Connection to Router Spoke C no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 101 interface Serial4/3 401 ! interface Serial4/3 ! Connection to the Hub Router no ip address encapsulation frame-relay clockrate 64000 frame-relay intf-type dce frame-relay route 201 interface Serial1/0 101 frame-relay route 301 interface Serial1/1 101 frame-relay route 401 interface Serial4/1 101 frame-relay route 501 interface Serial1/7 101