Frame Relay switching and point-to-point subinterfaces

Having browsed through half the Internet without finding any decent documentation on how to do this, I gave up on Google and put together something myself. Hopefully it can be useful for other networking students.

I’m doing a lab for Cisco CCNP ROUTE where you’re supposed to set up OSPF over a Frame Relay (NBMA) hub-and-spoke topology with a headquarter and two remote sites. All subinterfaces must be configured as point-to-point. This is how you configure the Frame Relay part.

Topology:

• DLCI 102 and 201 connecting R1_HQ and R2_EAST.
• DLCI 103 and 301 connecting R1_HQ and R4_WEST.
• R3_FR provides clocking signals (DCE) to the connected Frame Relay routers (DTE).

Configuration of the Frame Relay switch, R3_FR:

frame-relay switching
interface Serial0/0
 bandwidth 64
 no ip address
 encapsulation frame-relay IETF
 no ip route-cache
 clock rate 64000
 frame-relay intf-type dce
 frame-relay route 102 interface Serial0/1 201
 frame-relay route 103 interface Serial0/2 301
interface Serial0/1
 bandwidth 64
 no ip address
 encapsulation frame-relay IETF
 no ip route-cache
 clock rate 64000
 frame-relay intf-type dce
 frame-relay route 201 interface Serial0/0 102
interface Serial0/2
 bandwidth 64
 no ip address
 encapsulation frame-relay IETF
 no ip route-cache
 clock rate 64000
 frame-relay intf-type dce
 frame-relay route 301 interface Serial0/0 103


Configuring the R1_HQ router:

interface Serial0/0
bandwidth 64
no ip address
encapsulation frame-relay IETF
interface Serial0/0.102 point-to-point
ip address 10.1.1.1 255.255.255.252
frame-relay interface-dlci 102
interface Serial0/0.103 point-to-point
ip address 10.1.1.5 255.255.255.252
frame-relay interface-dlci 103

Configuring the R2_EAST router:

interface Serial0/0
bandwidth 64
no ip address
encapsulation frame-relay IETF
interface Serial0/0.201 point-to-point
ip address 10.1.1.2 255.255.255.252
frame-relay interface-dlci 201

Configuring the R4_WEST router:

interface Serial0/0
 bandwidth 64
 no ip address
 encapsulation frame-relay IETF
interface Serial0/0.301 point-to-point
 ip address 10.1.1.6 255.255.255.252
 frame-relay interface-dlci 301


HQ router can now ping both the EAST and WEST router.

Here’s how the Frame Relay switch see the topology:

R3_FR#show frame-relay route
Input Intf      Input Dlci      Output Intf     Output Dlci     Status
Serial0/0       102             Serial0/1       201             active
Serial0/0       103             Serial0/2       301             active
Serial0/1       201             Serial0/0       102             active
Serial0/2       301             Serial0/0       103             active

For more information check out “Comprehensive Guide to Configuring and Troubleshooting Frame Relay”:
http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml

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