David Sudjiman

This tutorial will discuss about single area ospf implementation on frame relay hub-and-spoke network using non-broadcast, broadcast, point-to-point, and point-to-multipoint.

Hub and spoke network using non-broadcast mode

On Hub and spoke (HnS) network, R2 can only send packets to R1 but not to R3. It goes the same for R3 being able to send packets R1 but not to R2. However, as only R1 has direct link to R2 and to R3, therefore R1 is suitable to be DR/BDR on non-broadcast mode.

Characteristics.

• Create Frame Relay (FR) mapping to ensure connection from R2 to R3 and vice versa.
• Make sure that only R1 has the priority to be DR/BDR.
• Hub and spoke topology on one subnet network.
• For Serial interface with Frame Relay encapsulation, the default network type is nonbroadcast. Therefore, command ip ospf network nonbroadcast is actually not necessary.
• Hello packet is sent every 30 seconds using Unicast addresses and link will be considered dead if not receiving Hello packet within 4 x 30 seconds (120 seconds).

Router 1

hostname R1
!
interface Serial0
 ip address 10.1.1.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network non-broadcast
 ip ospf priority 0
 frame-relay map ip 10.1.1.2 222
 frame-relay map ip 10.1.1.3 333
!
router ospf 1
 network 10.1.1.0 0.0.0.255 area 0

Router 2

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

Router 3

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

Hub and spoke network using broadcast mode

This scenario is not recommended as will clog the FR network with broadcast packets.

Characteristics.

• Create Frame Relay (FR) mapping to ensure connection from R2 to R3 and vice versa.
• Make sure that only R1 has the priority to be DR/BDR.
• Hub and spoke topology on one subnet network.
• For Serial interface with Frame Relay encapsulation, the default network type is nonbroadcast. Therefore, command ip ospf network broadcast is necessary.
• Hello packet is sent every 30 seconds using Unicast addresses and link will be considered dead if not receiving Hello packet within 4 x 30 seconds (120 seconds).

Basically the configuration remain similar with non-broadcast mode. However, the difference is only on command ip ospf network broadcast.

Hub and spoke network using point-to-point mode

On this scenario, the configuration is quite straightforward. All we need to pay attention is R1 as it acts as hub router to connect R2 and R3. Just create two subinterfaces and two subnet network for both side of network. Don’t forget to create DLCI mapping.

Characteristics.

• Create Frame Relay (FR) mapping to ensure connection from R2 to R3 and vice versa.
• No DR/BDR election.
• Hub and spoke topology on different subnet network.
• For subinterface with point-to-point mode, the default ospf network type is point-to-point.
• Hello packet is sent every 10 seconds using Multicast addresses and link will be considered dead if not receiving Hello packet within 4 x 10 seconds (40 seconds).

Router 1

hostname R1
!
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 point-to-point
 ip address 10.1.1.1 255.255.255.252
 ip ospf network point-to-point
 frame-relay interface-dlci 222
!
interface Serial0.2 point-to-point
 ip address 10.1.1.5 255.255.255.252
 ip ospf network point-to-point
 frame-relay interface-dlci 333
!
router ospf 1
 log-adjacency-changes
 network 10.1.1.0 0.0.0.3 area 0
 network 10.1.1.4 0.0.0.3 area 0

Router 2

hostname R2
!
interface Serial0
 no ip address
 encapsulation frame-relay
!
interface Serial0.1 point-to-point
 ip address 10.1.1.2 255.255.255.252
 ip ospf network point-to-point
 frame-relay interface-dlci 111
!
router ospf 1
 network 10.1.1.0 0.0.0.3 area 0

Router 3

hostname R3
!
interface Serial0
 no ip address
 encapsulation frame-relay
 frame-relay lmi-type cisco
!
interface Serial0.1 point-to-point
 ip address 10.1.1.6 255.255.255.252
 ip ospf network point-to-point
 frame-relay interface-dlci 111
!
router ospf 1
 log-adjacency-changes
 network 10.1.1.4 0.0.0.3 area 0

Hub and spoke network using point-to-multipoint mode

This point-to-multipoint mode will use one subnet for the whole network. The default mode for this is RFC 2328 (point-to-multipoint broadcast ) while Cisco standard uses point-to-multipoint non-broadcast.

Characteristics.

• Create Frame Relay (FR) mapping to ensure connection from R2 to R3 and vice versa.
• No DR/BDR election.
• Hub and spoke topology on same subnet.
• Hello packet is sent every 10 seconds using Multicast addresses and link will be considered dead if not receiving Hello packet within 4 x 10 seconds (40 seconds).

Router 1

hostname R1
!
interface Serial0
 ip address 10.1.1.1 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 frame-relay map ip 10.1.1.2 222
 frame-relay map ip 10.1.1.3 333
 frame-relay lmi-type cisco
!
router ospf 1
 log-adjacency-changes
 network 10.1.1.0 0.0.0.255 area 0

Router 2

hostname R2
!
interface Serial0
 ip address 10.1.1.2 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 frame-relay map ip 10.1.1.1 111
 frame-relay map ip 10.1.1.3 111
 frame-relay lmi-type cisco
!
router ospf 1
 log-adjacency-changes
 network 10.1.1.0 0.0.0.255 area 0

Router 3

hostname R3
!
interface Serial0
 ip address 10.1.1.3 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint
 frame-relay map ip 10.1.1.1 111
 frame-relay map ip 10.1.1.2 111
!
router ospf 1
 log-adjacency-changes
 network 10.1.1.0 0.0.0.255 area 0

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)