I had some pretty poor timing when I decided I wanted to take on this whole CCIE thing. Busy times at work etc, but surely I could shoehorn Lab study in there somewhere (can you hear my sarcasm via the interwebs?). But I’ve wanted this since I knew what a router was, so on we go…and on…and on…
But there’s one other reason it was poor timing – Frame Relay. My guess is if I had waited another couple of years it would have been dropped from the exam entirely. But I’m not a patient person, I want my CCIE, and I want it now. So Frame Relay it is. I uhm…don’t like Frame Relay too much. At all. But what doesn’t kill you makes you stronger, right?
So a topic that I stumbled with at first, since I have always done Frame from the CE point of view – Frame Relay Switching, a newer CCIE R&S topic in the last couple of years. It is an easy one to lab up and test in a three router topology using back-to-back Frame Relay – no need to build out a Frame Cloud.
Topology using R3 as the Frame Relay Switch
In this topology, R3 is playing the role of the frame-relay switch, with R1 and R2 as the clients using DLCI 103 and 203 respectively. To begin, R3 must have frame relay switching enabled globally:
R3(config)#frame-relay switching
Once switching has been enabled, the router’s interface type can be set to DCE (the default is DTE) so that it can respond to LMI queries and pass on DLCI information to R1 and R2. If frame-relay switching is not enabled prior to setting the interface type, an error message stating “Must enable frame-relay switching to configure DCE/NNI” will be generated. Clocking will need to be configured, and of course Frame Relay encapsulation must be enabled on both interfaces facing R1 and R2:
R3#show run int serial0/2/0
!
interface Serial0/2/0
description to R1 S0/3/1
no ip address
encapsulation frame-relay
clock rate 2000000
frame-relay intf-type dce
!
R3#show run int serial0/2/1
!
interface Serial0/2/1
description to R2 S0/0/1
no ip address
encapsulation frame-relay
clock rate 2000000
frame-relay intf-type dce
end
Likewise, R1 and R2 must have their interfaces configured for frame-relay encapsulation, as well as their assigned IP addresses:
R1#sh run int s0/3/1
!
interface Serial0/3/1
description R3 S0/2/0
ip address 172.16.10.1 255.255.255.0
encapsulation frame-relay
end
R1#
R2#sh run int s0/3/1
!
interface Serial0/0/1
description R3 S0/2/1
ip address 172.16.10.2 255.255.255.0
encapsulation frame-relay
end
In this scenario, no DLCIs are locally terminated on R3 – they will be switched to other Frame Relay ports, specifically between R1 and R2. There are two methods that can be used to accomplish this. The frame-relay route interface-level command, which is a legacy command, or the globally configured connect command. First, using the frame-relay route command, the incoming DLCI on an interface must be statically mapped to an outgoing interface and outgoing DLCI, and then configured in reverse:
R3#sh run int s0/2/0
!
interface Serial0/2/0
description to R1 S0/3/1
no ip address
encapsulation frame-relay
clock rate 2000000
frame-relay intf-type dce
frame-relay route 103 interface Serial0/2/1 203
end
R3#sh run int s0/2/1
!
interface Serial0/2/1
description to R2 S0/0/1
no ip address
encapsulation frame-relay
clock rate 2000000
frame-relay intf-type dce
frame-relay route 203 interface Serial0/2/0 103
end
Once this has been configured, switched PVCs should become active on R3:
R3#show frame-relay pvc
PVC Statistics for interface Serial0/2/0 (Frame Relay DCE)
Active Inactive Deleted Static
Local 0 0 0 0
Switched 1 0 0 0
Unused 0 0 0 0
DLCI = 103, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial0/2/0
….[output omitted]…
PVC Statistics for interface Serial0/2/1 (Frame Relay DCE)
Active Inactive Deleted Static
Local 0 0 0 0
Switched 1 0 0 0
Unused 0 0 0 0
DLCI = 203, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial0/2/1
….[output omitted]…
Connectivity can be further verified on both R1 and R2 with show frame-relay pvc, show frame-relay map, and a ping test:
R1#show frame-relay pvc
PVC Statistics for interface Serial0/3/1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 103, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/3/1
….[output omitted]…
R1#show frame-relay map
Serial0/3/1 (up): ip 172.16.10.2 dlci 103(0x67,0x1870), dynamic,
broadcast,, status defined, active
R1#ping 172.16.10.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
R1#
On R2:
R2#show frame-relay pvc
PVC Statistics for interface Serial0/0/1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 203, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/1
….[output omitted]…
R2#show frame-relay map
Serial0/0/1 (up): ip 172.16.10.1 dlci 203(0xCB,0x30B0), dynamic,
broadcast,, status defined, active
R2#ping 172.16.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms
The second method, using the global connect command, can be configured as follows:
R3(config)# connect R1_switched_R2 Serial0/2/0 103 Serial0/2/1 203
Once completed, the same verification tools can be used again on R3, R1 and R2:
R3#show frame-relay pvc
PVC Statistics for interface Serial0/2/0 (Frame Relay DCE)
Active Inactive Deleted Static
Local 0 0 0 0
Switched 1 0 0 0
Unused 0 0 0 0
DLCI = 103, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial0/2/0
….[output omitted]…
PVC Statistics for interface Serial0/2/1 (Frame Relay DCE)
Active Inactive Deleted Static
Local 0 0 0 0
Switched 1 0 0 0
Unused 0 0 0 0
DLCI = 203, DLCI USAGE = SWITCHED, PVC STATUS = ACTIVE, INTERFACE = Serial0/2/1
….[output omitted]…
On R1:
R1#show frame-relay pvc
PVC Statistics for interface Serial0/3/1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 103, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/3/1
….[output omitted]…
R1#show frame-relay map
Serial0/3/1 (up): ip 172.16.10.2 dlci 103(0x67,0x1870), dynamic,
broadcast,, status defined, active
R1#ping 172.16.10.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms
R1#
On R2:
R2#show frame-relay pvc
PVC Statistics for interface Serial0/0/1 (Frame Relay DTE)
Active Inactive Deleted Static
Local 1 0 0 0
Switched 0 0 0 0
Unused 0 0 0 0
DLCI = 203, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/1
….[output omitted]…
R2#show frame-relay map
Serial0/0/1 (up): ip 172.16.10.1 dlci 203(0xCB,0x30B0), dynamic,
broadcast,, status defined, active
R2#ping 172.16.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.10.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms
