You want to configure the router to support Frame Relay SVCs.
Frame Relay SVCs are not extremely common, but some carrier networks support them. The advantage to using SVCs is that the router can add and remove inactive virtual circuits dynamically in a lightly used network. Because of the extra complexity and the management problems associated with dynamic network topologies, most network engineers will only use this feature if it offers significant cost advantages.
You can configure SVCs to use subinterfaces as in Recipe 10.1:
Central#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Central(config)#interface Serial0 Central(config-if)#encapsulation frame-relay Central(config-if)#frame-relay lmi-type q933a Central(config-if)#frame-relay svc Central(config-if)#exit Central(config)#interface Serial0.10 point-to-point Central(config-subif)#ip address 192.168.1.129 255.255.255.252 Central(config-subif)#frame-relay interface-dlci 100 Central(config-subif)#map-group SVCMAP Central(config-fr-dlci)#class SVCclass Central(config-fr-dlci)#exit Central(config-subif)# exit Central(config)#map-list SVCMAP source-addr X121 1234 dest-addr X121 4321 Central(config-map-list)#ip 192.168.55.6 class SVCclass ietf Central(config-map-list)#exit Central(config)#map-class frame-relay SVCclass Central(config-map-class)#frame-relay traffic-rate 56000 128000 Central(config-map-class)#end Central#
You can also configure Frame Relay SVCs using map statements, similar to Recipe 10.3:
Central#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Central(config)#interface Serial Central(config-if)#ip address 192.168.55.1 255.255.255.0 Central(config-if)#encapsulation frame-relay Central(config-if)#frame-relay lmi-type q933a Central(config-if)#frame-relay svc Central(config-if)#map-group SVCMAP Central(config-if)#frame-relay interface-dlci 50 Central(config-fr-dlci)#class SVCclass Central(config-fr-dlci)#exit Central(config-if)#exit Central(config)#map-list SVCMAP source-addr X121 1234 dest-addr X121 4321 Central(config-map-list)#ip 192.168.55.6 class SVCclass ietf Central(config-map-list)#exit Central(config)#map-class frame-relay SVCclass Central(config-map-class)#frame-relay traffic-rate 56000 128000 Central(config-map-class)#end Central#
You can enable Frame Relay SVCs on an interface simply by including the frame-relay svc command. This is required whether you use maps or subinterfaces:
Central(config-if)#frame-relay svc
However, this doesn't tell the network how to actually build the virtual circuits. To do that, you need to define a map list and a map class:
Central(config)#map-list SVCMAP source-addr X121 1234 dest-addr X121 4321 Central(config-map-list)#ip 192.168.55.6 class SVCclass ietf Central(config-map-list)#exit Central(config)#map-class frame-relay SVCclass Central(config-map-class)#frame-relay traffic-rate 56000 128000 Central(config-map-class)#end
The map list associates an IP address with either X.121 or E.164 source and destination addresses. We have used X.121 addresses in the example, but if your carrier's network uses E.164 addressing instead, you can simply replace the keyword X121 with E164 and specify the appropriate E.164 addresses:
Central(config)#map-list SVCMAP source-addr E164 1234 dest-addr E164 4321
The map-class command tells the router about the actual SVC parameters such as CIR and EIR. In this example, we want the network to create SVCs with CIR of 56,000 and total burst rate (CIR+EIR) of 128,000 bits per second.
By default, the router will keep an idle SVC for 120 seconds before tearing it down. You can change this period using the frame-relay idle-timer command. There are three ways to specify an idle time. You can have the router tear down an idle PVC if there is no traffic in either direction for a specified time period like this:
Central(config)#map-class frame-relay SVCclass Central(config-map-class)#frame-relay idle-timer 60
Or you can specify the inbound and outbound directions separately:
Central(config)#map-class frame-relay SVCclass Central(config-map-class)#frame-relay idle-timer in 20 Central(config-map-class)#frame-relay idle-timer out 30
In each case, the argument is the time period specified in seconds.
You can view the SVC map information on a router with the show frame-relay svc command:
Central#show frame-relay svc maplist SVCMAP
Map List : SVCMAP
Address : Source X121 1234 <----> Destination X121 4321
Protocol : ip 192.168.55.6 Encapsulation : IETF
FMIF (Frame Mode Information Field Size), bytes
Configured : In = 1500, Out = 1500
CIR (Committed Information Rate), bits/sec
Configured : In = 56000, Out = 56000,
Minimum Acceptable CIR, bits/sec
Configured : In = 56000, Out = 56000,
Bc (Committed Burst Size), bits
Configured : In = 56000, Out = 56000,
Be (Excess Burst Size), bits
Configured : In = 56000, Out = 56000,
Central#
Remember that whether you use maps or subinterfaces, you can combine SVCs and PVCs on the same physical interface.
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