Frame-Relay Switching

So today I wanna talk about "Nasty Frame-Relay Switching Stuff". I mean if you are a CCIE R&S Version 4 student then you need to know this stuff now. In Ver 3 blueprint the FR Switch in lab was always preconfigured. Although there were some Pitfalls associated with those initial configurations to test your Frame-Relay skills like some extra DLCIs configured which were not required or in other words to add some more fun into section like OSPF over FR.

 Take a look at diagram below. Here routers R1, R2 & R3 are connected to another router in middle which is acting as a Frame-Relay Switch < :-) Yes you can configure even a router as a Frame-Relay Switch>. R1 is acting as Hub and connected to R2/R3 which are acting as Spoke Routers. Also there is no Direct DLCI between R2 & R3.

Now lets hop on to the command line and review the necessary configuration required on each device. Later we will discuss the theory along with some verification stuff.

R1#
!
interface Serial1/0
 ip address 10.0.0.1 255.255.255.0
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay map ip 10.0.0.1 103
 frame-relay map ip 10.0.0.3 103 broadcast
 frame-relay map ip 10.0.0.2 102 broadcast
 no frame-relay inverse-arp
 !
--------------------------------------
R2#
!
interface Serial1/0
 ip address 10.0.0.2 255.255.255.0
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay map ip 10.0.0.2 201
 frame-relay map ip 10.0.0.3 201
 frame-relay map ip 10.0.0.1 201 broadcast
 no frame-relay inverse-arp
 !
--------------------------------------
R3#
!
interface Serial1/0
 ip address 10.0.0.3 255.255.255.0
 encapsulation frame-relay
 serial restart-delay 0
 frame-relay map ip 10.0.0.3 301
 frame-relay map ip 10.0.0.2 301
 frame-relay map ip 10.0.0.1 301 broadcast
 no frame-relay inverse-arp
 !
--------------------------------------
Now lets take a look at FRswitch configuration and discuss little bit about it:


FRswitch#
!
interface Serial1/0
 no ip address -> No IP address needs to be configured
 encapsulation frame-relay ->Enabling WAN Encapsulation FR
 logging event subif-link-status ->Optional
 logging event dlci-status-change ->Optional
 serial restart-delay 0
 clock rate 64000 -> Setting Up clock rate on DCE side
 no frame-relay inverse-arp
 frame-relay intf-type dce -> Configuring FR interface as DCE type
 frame-relay route 102 interface Serial1/1 201 ->If Data received on DLCI 102 then it will be sent over to interface serial1/1 over DLCI 201 <- Mapping Incoming DLCI to Outgoing DLCI ->
 frame-relay route 103 interface Serial1/2 301 ->Same Logic as explained above
 !
!
interface Serial1/1
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 clock rate 64000
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 201 interface Serial1/0 102
 !
!
interface Serial1/2
 no ip address
 encapsulation frame-relay
 serial restart-delay 0
 clock rate 64000
 no frame-relay inverse-arp
 frame-relay intf-type dce
 frame-relay route 301 interface Serial1/0 103
 !

So all frame relay switch doing is routing traffic at layer 2. It's more like Air traffic controller guy who knows if a plane comes on certain track then he has to route it to another predefined track. Of course "No chances for error" there

Now lets do the verification:


FRswitch#sh frame route
Input Intf      Input Dlci      Output Intf     Output Dlci     Status
Serial1/0       102             Serial1/1       201             active
Serial1/0       103             Serial1/2       301             active
Serial1/1       201             Serial1/0       102             active
Serial1/2       301             Serial1/0       103             active


R1#sh frame map
Serial1/0 (up): ip 10.0.0.2 dlci 102(0x66,0x1860), static,
              broadcast,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.1 dlci 103(0x67,0x1870), static,
               broadcast,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.3 dlci 103(0x67,0x1870), static,
              broadcast,
              CISCO, status defined, active


R2#sh frame map
Serial1/0 (up): ip 10.0.0.2 dlci 201(0xC9,0x3090), static,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.3 dlci 201(0xC9,0x3090), static,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.1 dlci 201(0xC9,0x3090), static,
              broadcast,
              CISCO, status defined, active


R3#sh frame map
Serial1/0 (up): ip 10.0.0.3 dlci 301(0x12D,0x48D0), static,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.2 dlci 301(0x12D,0x48D0), static,
              CISCO, status defined, active
Serial1/0 (up): ip 10.0.0.1 dlci 301(0x12D,0x48D0), static,
              broadcast,
              CISCO, status defined, active


R2#ping 10.0.0.1 r 1

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 160/160/160 ms
R2#ping 10.0.0.2 r 1

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 624/624/624 ms
R2#ping 10.0.0.3 r 1

Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 10.0.0.3, timeout is 2 seconds:
!
Success rate is 100 percent (1/1), round-trip min/avg/max = 536/536/536 ms
R2#

Best Regards,

Deepak Arora