Configuring FRF.5 Network Interworking
This section discusses the configuration tasks required to enable Frame Relay network interworking (FRF.5) on the Cisco router. The network, consisting of four routers and an ATM LS1010 switch, is depicted in Figure 8-15 and is used to illustrate the configuration examples in this section. Note that R2 and R3 belong to the supported Cisco platforms required for Frame Relay to ATM Interworking.
Figure 8-15. Simple Network to Illustrate the Configuration Examples for FRF.5
R2 and R3 in Figure 8-15 are the routers performing the FRF.5 network interworking function between the Frame Relay and the ATM networks. To enable FRF.5 on R2 or R3 using one-to-one multiplexing, follow the configuration steps listed below:
Step 1. Enter the interface configuration mode of the serial interface connected to the Frame Relay network with the interface serial number command and enable Frame Relay encapsulation with the encapsulation frame-relay command.
Step 2. If the incoming Frame Relay PVC is a switched VC, identify it with the frame-relay interface-dlci dlci switched interface configuration command. If the incoming Frame Relay PVC is a terminated VC, this step is not required.
Step 3. Configure the ATM interface connected to the ATM network and enter the interface configuration mode with the interface atm number command.
Step 4. Create the ATM PVC with the VPI/VCI pair using pvc [pvc-name] vpi/vci interface configuration command. The ATM PVC can be identified using a pvc-name but it is optional. The VPI/VCI value is usually assigned by the provider and configured on the ATM switch.
Step 5. Configure the ATM adaptation layer and encapsulation type for the ATM PVC with the encapsulation aal5mux frame-relay command. The aal5mux encapsulation has slightly less overhead compared with the default aal5snap encapsulation. The aal5mux encapsulation is usually used to dedicate the specified PVC to only a single protocol.
Step 6. Create a connection to connect the Frame Relay DLCI to the ATM PVC using the connect connection-name FR-interface FR-DLCI ATM-interface ATM-PVC network-interworking global configuration command. The network-interworking option is specified to indicate that FRF.5 is to be used.
Step 7. (optional) Under the FRF.5 mode, set the ATM CLP bit for traffic in the Frame Relay to ATM direction using the clp-bit {0 | 1 | map-de} command. As you saw earlier, the default configuration is clp-bit map-de. (Note that this command is presently available on Cisco MC3810, 2600, and 3600 series routers only.)
Step 8. (optional) Under the FRF.5 mode, set the DE bit for traffic in the ATM to Frame Relay direction using the de-bit map-clp command. This is the default. Use the no form of the command to disable CLP bit to DE bit mapping. (Note that this command is presently available on Cisco MC3810, 2600, and 3600 series routers only.)
Step 9. To enable the FRF.5 network interworking connection, perform no shutdown. Use the shutdown command to disconnect the FRF.5 network interworking connection.
Example 8-8 below shows the complete FRF.5 configuration on routers R2 and R3.
Example 8-8. Configuration on R2 and R3 (One-to-One Connection)
! R2:
<output omitted>
!
interface Serial1/3
no ip address
encapsulation frame-relay
frame-relay interface-dlci 16 switched
!
interface ATM3/0
no ip address
no ip route-cache
no atm ilmi-keepalive
pvc 1/32
encapsulation aal5mux frame-relay
!
connect frf5 Serial1/3 16 ATM3/0 1/32 network-interworking
clp-bit map-de
! R3
<output omitted>
!
interface Serial1
no ip address
encapsulation frame-relay
frame-relay interface-dlci 26 switched
!
interface ATM0
no ip address
no atm ilmi-keepalive
pvc 1/32
encapsulation aal5mux frame-relay
!
connect frf5 Serial1 26 ATM0 1/32 network-interworking
de-bit map-clp
This section looks at how many-to-one multiplexing is configured for FRF.5 network interworking. In Figure 8-15, two Frame Relay PVCs are provisioned on each service user at each of the Frame Relay networks. A vc-group command has to be created to assign multiple Frame Relay DLCIs to one ATM VC. The configuration tasks required for enabling many-to-one multiplexing are almost the same as the one-to-one case presented previously. As such, only the additional configuration commands necessary for configuring many-to-one multiplexing are explained.
Step 1. Configure a VC group to assign multiple Frame Relay DLCIs to a single ATM VC using the vc-group group-name global configuration command.
Step 2. In the vc-group configuration mode, specify the Frame Relay DLCIs and map them to the Frame Relay SSCS DLCIs using the FR-interface FR-DLCI FR-SSCS-DLCI vc-group configuration command. Note that both the FR-DLCI and FR-SSCS-DLCI are required.
Step 3. Create a connection to connect the VC group to the ATM PVC using connect connection-name vc-group group-name ATM-interface ATM-PVC network-interworking global configuration command.
Figure 8-15. Simple Network to Illustrate the Configuration Examples for FRF.5
R2 and R3 in Figure 8-15 are the routers performing the FRF.5 network interworking function between the Frame Relay and the ATM networks. To enable FRF.5 on R2 or R3 using one-to-one multiplexing, follow the configuration steps listed below:
Step 1. Enter the interface configuration mode of the serial interface connected to the Frame Relay network with the interface serial number command and enable Frame Relay encapsulation with the encapsulation frame-relay command.
Step 2. If the incoming Frame Relay PVC is a switched VC, identify it with the frame-relay interface-dlci dlci switched interface configuration command. If the incoming Frame Relay PVC is a terminated VC, this step is not required.
Step 3. Configure the ATM interface connected to the ATM network and enter the interface configuration mode with the interface atm number command.
Step 4. Create the ATM PVC with the VPI/VCI pair using pvc [pvc-name] vpi/vci interface configuration command. The ATM PVC can be identified using a pvc-name but it is optional. The VPI/VCI value is usually assigned by the provider and configured on the ATM switch.
Step 5. Configure the ATM adaptation layer and encapsulation type for the ATM PVC with the encapsulation aal5mux frame-relay command. The aal5mux encapsulation has slightly less overhead compared with the default aal5snap encapsulation. The aal5mux encapsulation is usually used to dedicate the specified PVC to only a single protocol.
Step 6. Create a connection to connect the Frame Relay DLCI to the ATM PVC using the connect connection-name FR-interface FR-DLCI ATM-interface ATM-PVC network-interworking global configuration command. The network-interworking option is specified to indicate that FRF.5 is to be used.
Step 7. (optional) Under the FRF.5 mode, set the ATM CLP bit for traffic in the Frame Relay to ATM direction using the clp-bit {0 | 1 | map-de} command. As you saw earlier, the default configuration is clp-bit map-de. (Note that this command is presently available on Cisco MC3810, 2600, and 3600 series routers only.)
Step 8. (optional) Under the FRF.5 mode, set the DE bit for traffic in the ATM to Frame Relay direction using the de-bit map-clp command. This is the default. Use the no form of the command to disable CLP bit to DE bit mapping. (Note that this command is presently available on Cisco MC3810, 2600, and 3600 series routers only.)
Step 9. To enable the FRF.5 network interworking connection, perform no shutdown. Use the shutdown command to disconnect the FRF.5 network interworking connection.
Example 8-8 below shows the complete FRF.5 configuration on routers R2 and R3.
Example 8-8. Configuration on R2 and R3 (One-to-One Connection)
! R2:
<output omitted>
!
interface Serial1/3
no ip address
encapsulation frame-relay
frame-relay interface-dlci 16 switched
!
interface ATM3/0
no ip address
no ip route-cache
no atm ilmi-keepalive
pvc 1/32
encapsulation aal5mux frame-relay
!
connect frf5 Serial1/3 16 ATM3/0 1/32 network-interworking
clp-bit map-de
! R3
<output omitted>
!
interface Serial1
no ip address
encapsulation frame-relay
frame-relay interface-dlci 26 switched
!
interface ATM0
no ip address
no atm ilmi-keepalive
pvc 1/32
encapsulation aal5mux frame-relay
!
connect frf5 Serial1 26 ATM0 1/32 network-interworking
de-bit map-clp
This section looks at how many-to-one multiplexing is configured for FRF.5 network interworking. In Figure 8-15, two Frame Relay PVCs are provisioned on each service user at each of the Frame Relay networks. A vc-group command has to be created to assign multiple Frame Relay DLCIs to one ATM VC. The configuration tasks required for enabling many-to-one multiplexing are almost the same as the one-to-one case presented previously. As such, only the additional configuration commands necessary for configuring many-to-one multiplexing are explained.
Step 1. Configure a VC group to assign multiple Frame Relay DLCIs to a single ATM VC using the vc-group group-name global configuration command.
Step 2. In the vc-group configuration mode, specify the Frame Relay DLCIs and map them to the Frame Relay SSCS DLCIs using the FR-interface FR-DLCI FR-SSCS-DLCI vc-group configuration command. Note that both the FR-DLCI and FR-SSCS-DLCI are required.
Step 3. Create a connection to connect the VC group to the ATM PVC using connect connection-name vc-group group-name ATM-interface ATM-PVC network-interworking global configuration command.
