Configuring Frame Point-to-Point Sub-Interfaces
You can configure multiple point to point sub-interfaces using a single physical Frame Frame circuit. This type of configuration can be used between hub and spoke sites where you would want to keep the spokes in their own layer 3 subnet’s. This lab will discuss and demonstrate the frame relay point to point sub-interface configuration and verification.
Real World Application & Core Knowledge
Now that you’re familiar with Point-to-Point Frame Relay links lets take a step further and demonstrate how you can have multiple frame relay links on a single router using a single physical interface but multiple sub-interfaces to represent the multiple PVC’s (Permanent Virtual Circuits)
By Creating a Point-to-Point Sub-interface which will have an interface-dlci assigned to it you’ll have the ability for R1 to communicate to R2 and R3 as if R1 has two completely separate point-to-point links using only a single physical link to the Frame Relay cloud.
When creating a Sub-interface for interface-dlci’s it is a fairly common practice to use the DLCI number as the sub-interface number for documentation purposes however this is not a requirement.
In this lab you’ll familiarize yourself with the following new commands;
| Command | Description |
|---|---|
| interface Serial#/#.### point-to-point | This command when in global configuration creates a new point-to-point sub-interface that can be used to configure interface dlci’s. |
Lab Prerequisites
- If you are using GNS3 than load the Free CCNA Workbook GNS3 topology than start devices; R1, R2 and R3.
- Establish a console session with devices R1, R2 and R3 than configure the devices respected hostname(s).
- Configure R1, R2 and R3’s Serial0/0 interface encapsulation to frame relay and enable the interfaces using the no shut command.
Lab Objectives
- On R1, create the sub-interface Serial0/0.122 and assign it the interface DLCI of 122 and the IP Address of 172.18.12.1/30 then create interface Serial0/0.123 and assign it the IP Address 172.18.13.1/30
- On R2, create the sub-interface Serial0/0.221 and assign it the interface DLCI of 221 and the IP Address of 172.18.12.2/30
- On R3, create the sub-interface Serial0/0.321 and assign it the interface DLCI of 321 and the IP Address of 172.18.13.2/30
- Verify connectivity using the show frame-relay pvc and ping commands on R1.
Lab Instruction
Objective 1. – On R1, create the sub-interface Serial0/0.122 and assign it the interface DLCI of 122 and the IP Address of 172.18.12.1/30 then create interface Serial0/0.123 and assign it the ip address 172.18.13.1/30
R1 con0 is now available Press RETURN to get started. R1>enable R1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R1(config)#interface Serial0/0.122 point-to-point R1(config-subif)#ip address 172.18.12.1 255.255.255.252 R1(config-subif)#frame-relay interface-dlci 122 R1(config-fr-dlci)#exit R1(config-subif)#interface Serial0/0.123 point-to-point R1(config-subif)#ip address 172.18.13.1 255.255.255.252 R1(config-subif)#frame-relay interface-dlci 123 R1(config-subif)#end R1# %SYS-5-CONFIG_I: Configured from console by console R1#
Objective 2. – On R2, create the sub-interface Serial0/0.221 and assign it the interface DLCI of 221 and the IP Address of 172.18.12.2/30
R2 con0 is now available Press RETURN to get started. R2>enable R2#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R2(config)#interface Serial0/0.221 point-to-point R2(config-subif)#ip add 172.18.12.2 255.255.255.252 R2(config-subif)#frame-relay interface-dlci 221 R2(config-fr-dlci)#end R2# %SYS-5-CONFIG_I: Configured from console by console R2#
Objective 3. – On R3, create the sub-interface Serial0/0.321 and assign it the interface DLCI of 321 and the IP Address of 172.18.13.2/30
R3 con0 is now available Press RETURN to get started. R3>enable R3#configure terminal Enter configuration commands, one per line. End with CNTL/Z. R3(config)#interface Serial0/0.321 point-to-point R3(config-subif)#ip add 172.18.13.2 255.255.255.252 R3(config-subif)#frame-relay interface-dlci 321 R3(config-fr-dlci)#end R3# %SYS-5-CONFIG_I: Configured from console by console R3#
Objective 4. – Verify connectivity using the show frame-relay pvc and ping commands on R1.
R1#show frame-relay pvc PVC Statistics for interface Serial0/0 (Frame Relay DTE) Active Inactive Deleted Static Local 2 0 0 0 Switched 0 0 0 0 Unused 2 0 0 0 DLCI = 122, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0.122 input pkts 20 output pkts 19 in bytes 5395 out bytes 5187 dropped pkts 0 in pkts dropped 0 out pkts dropped 0 out bytes dropped 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 14 out bcast bytes 4667 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec pvc create time 00:14:33, last time pvc status changed 00:14:33 DLCI = 123, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0.123 input pkts 22 output pkts 20 in bytes 6045 out bytes 4380 dropped pkts 0 in pkts dropped 0 out pkts dropped 0 out bytes dropped 0 in FECN pkts 0 in BECN pkts 0 out FECN pkts 0 out BECN pkts 0 in DE pkts 0 out DE pkts 0 out bcast pkts 10 out bcast bytes 3340 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec pvc create time 00:17:27, last time pvc status changed 00:17:27 R1#ping 172.18.12.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.18.12.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 8/82/188 ms R1#ping 172.18.13.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.18.13.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 28/96/168 ms R1#
