David Sudjiman

This is the answer from Scenario 3: Single Area OSPF on Frame Relay network. As this is not the only way to implement OSPF routing, yours may vary.

Router 1

hostname R1
!
interface Serial0
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.1.1.1 255.255.255.0
 ip ospf priority 1
 frame-relay map ip 10.1.1.2 222 broadcast
 frame-relay map ip 10.1.1.3 333 broadcast
!
interface Serial0.2 point-to-point
 ip address 20.2.2.1 255.255.255.0
 ip ospf priority 0
 frame-relay interface-dlci 444
!
router ospf 1
 network 10.1.1.0 0.0.0.255 area 0
 network 20.2.2.0 0.0.0.255 area 0
 neighbor 10.1.1.3
 neighbor 10.1.1.2

Router 2

hostname R2
!
interface Serial0
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.1.1.2 255.255.255.0
 ip ospf priority 0
 frame-relay map ip 10.1.1.1 111 broadcast
 frame-relay map ip 10.1.1.3 333 broadcast
!
router ospf 1
 network 10.1.1.0 0.0.0.255 area 0

Router 3

hostname R3
!
interface Serial0
 encapsulation frame-relay
!
interface Serial0.1 multipoint
 ip address 10.1.1.3 255.255.255.0
 ip ospf priority 0
 frame-relay map ip 10.1.1.1 111 broadcast
 frame-relay map ip 10.1.1.2 222 broadcast
!
router ospf 1
 network 10.1.1.0 0.0.0.255 area 0

Router 4

hostname R4
!
interface Serial0
 encapsulation frame-relay
!
interface Serial0.1 point-to-point
 ip address 20.2.2.2 255.255.255.0
 frame-relay interface-dlci 111
!
router ospf 1
 network 20.2.2.0 0.0.0.255 area 0

From the above configurations, we can notify that:

• R1 serial interface 0.1 is the set to ip ospf priority 1 while others are ip ospf priority 0. This command will make Router 1 as DR. Why are we using R1 as DR? This is just because R1 is accessible from either R2, R3, and R4.
• R1 interface s0.1 uses ip ospf network non-broadcast. This we can see from command sh ip ospf int s0.1. Why it is not shown on sh run configuration? because ip ospf network non-broadcast is default for serial interface with frame relay encapsulation and s0.1 uses multipoint mode.

R1#sh ip ospf int s0.1
Serial0.1 is up, line protocol is up
  Internet Address 10.1.1.1/24, Area 0
  Process ID 1, Router ID 20.2.2.1, Network Type NON_BROADCAST, Cost: 64
  Transmit Delay is 1 sec, State DR, Priority 1
  Designated Router (ID) 20.2.2.1, Interface address 10.1.1.1
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    Hello due in 00:00:29
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 4 msec, maximum is 4 msec
  Neighbor Count is 2, Adjacent neighbor count is 2
    Adjacent with neighbor 10.1.1.3
    Adjacent with neighbor 10.1.1.2
  Suppress hello for 0 neighbor(s)

• R1 interface s0.2 uses ip ospf network point-to-point. This we can see from command sh ip ospf int s0.2. Why it is not shown on sh run configuration? because ip ospf network point-to-point is default for serial interface with frame relay encapsulation and s0.2 uses point-to-point mode.

R1#sh ip ospf int s0.2
Serial0.2 is up, line protocol is up
  Internet Address 20.2.2.1/24, Area 0
  Process ID 1, Router ID 20.2.2.1, Network Type POINT_TO_POINT, Cost: 64
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:06
  Index 2/2, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 1, maximum is 1
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 20.2.2.2
  Suppress hello for 0 neighbor(s)

• R1 Router ID (RID) is 20.2.2.1

Sources

• Cisco System 2006, Configuring OSPF, viewed 15 May 2006, http://www.cisco.com/…[cut]…chapter09186a00800b3f2e.html
  
• Gough, C 2005, CCNP BSCI Exam Certification Guide 3rd Edn., Cisco Press, Indianapolis. (ISBN: 1587200856)
• Sudjiman, D 2006, Single Area OSPF on Frame Relay Full Mesh Network, viewed 15 May 2006, http://www.davidsudjiman.info/?p=104
• Sudjiman, D 2006, Single Area OSPF on Frame Relay Hub-and-Spoke Network, viewed 15 May 2006, http://www.davidsudjiman.info/?p=105