Sunday, August 29, 2010

BSCI - OSPF - Network Types - Point-to-Multipoint

Point-to-Multipoint

  • Full mesh not required
  • Allows for NBMA networking
  • No DR/BDR elections
  • Timers = 30 seconds /120 seconds
  • Do not need to manually configure neighbor statements
  • Specific networks advertised through out.
    Configuration:
    Lacking a diagram, assume we have 4 routers in a hub and spoke design. R1 is the Hub and R2,R3, and R4 are spoke routers. Frame-relay is in use.

    On R1:
    R1(config)#router ospf 1
    R1(config-router)#network 192.168.1.0 0.0.0.255 area 0
    !
    R1(config)#int s0/0
    R1(config-if)#ip address 192.168.1.1 255.255.255.0
    R1(config-if)#encapsulation frame-relay
    R1(config-if)#ip ospf network point-to-multipoint
    R1(config-if)#frame-relay map ip 192.168.1.2 102^
    R1(config-if)#frame-relay map ip 192.168.1.3 103
    R1(config-if)#frame-relay map ip 192.168.1.4 104
    !
    ^ maps 192.168.1.2 to DLCI 102 - this is locally significant.

    On R2:
    R2(config)#router ospf 1
    R2(config-router)#network 192.168.1.0 0.0.0.255 area 0
    !
    R2(config)#int s0/0
    R2(config-if)#ip address 192.168.1.2 255.255.255.0
    R2(config-if)#encapsulation frame-relay
    R2(config-if)#ip ospf network point-to-multipoint
    R2(config-if)#frame-relay map ip 192.168.1.1 25
    R2(config-if)#frame-relay map ip 192.168.1.3 25
    R2(config-if)#frame-relay map ip 192.168.1.4 25
    !

    On R3:
    R3(config)#router ospf 1
    R3(config-router)#network 192.168.1.0 0.0.0.255 area 0
    !
    R3(config)#int s0/0
    R3(config-if)#ip address 192.168.1.3 255.255.255.0
    R3(config-if)#encapsulation frame-relay
    R3(config-if)#ip ospf network point-to-multipoint
    R3(config-if)#frame-relay map ip 192.168.1.1 35
    R3(config-if)#frame-relay map ip 192.168.1.2 35
    R3(config-if)#frame-relay map ip 192.168.1.4 35
    !

    On R4:
    R4(config)#router ospf 1
    R4(config-router)#network 192.168.1.0 0.0.0.255 area 0
    !
    R4(config)#int s0/0
    R4(config-if)#ip address 192.168.1.4 255.255.255.0
    R4(config-if)#encapsulation frame-relay
    R4(config-if)#ip ospf network point-to-multipoint
    R4(config-if)#frame-relay map ip 192.168.1.1 45
    R4(config-if)#frame-relay map ip 192.168.1.2 45
    R4(config-if)#frame-relay map ip 192.168.1.3 45
    !

    Note - the lack of manually assigned neighbor statements and the fact you still need to configure your frame-relay maps.
    -Also do not forget the ip ospf network point-to-multipoint cmd.

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