Module 3 - Implementing OSPF in an NBMA Network ppt

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BSCI Module 3 Lesson 5 - Implementing OSPF in
an NBMA Network
OSPF
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Objective
 Configuring the OSPF Network Type
 Configuring OSPF over Frame Relay
 Using the neighbor Command
 The show ip ospf neighbor Command
 Point-to-Multipoint Configuration
 Point-to-Multipoint Nonbroadcast Configuration
 Using Subinterfaces in OSPF over a Frame Relay
Configuration
 Configuring a Point-to-Point Subinterface
 Configuring a Multipoint Subinterface
 OSPF over NBMA Topology Summary
 Tracking OSPF Adjacencies
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Configuring OSPF over Frame Relay
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RFC-compliant Non-broadcast Mode
 One IP subnet.
 Neighbors must be manually
configured.
 DR and BDR elected.
 DR and BDR need to have full
connectivity with all other
routers.
 Typically used in a full mesh
topology.
RTB(config-if)#ip ospf network non-broadcast

RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0
RTB(config-router)#neighbor 3.1.1.1
RTB(config-router)#neighbor 3.1.1.3
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The neighbor command options
Option Description
priority number
Specifies the priority of neighbor. Default is zero,
which means neighbor can never be DR.
poll-interval
number
Amount of time a NBMA interface waits before
sending hellos to the neighbor even if the neighbor is
inactive.
cost number

Assigns a cost to the neighbor from 1 to 65535.
Neighbors with no specific cost configured will
assume the cost of the interface, based on the ip
ospf cost command. (Not used with NBMA)
database-filter all
Filters outgoing LSAs to an OSPF neighbor
neighbor ip-address [priority number] [poll-interval
number] [cost number] [database-filter all]
Router(config-router)#
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Neighbor command example
 NOTE: If RB&RC is configured with priority 1 or above
RA will see RB&RC as priority 1 in neighbor table
regardless the “neighbor priority 0” command
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The show ip ospf neighbor Command
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RFC-compliant Point-to-Multipoint Mode
 One IP subnet.
 Uses multicast OSPF hello
packet to automatically

discover neighbors.
 DR and BDR not required
 Typically used in a partial-
mesh or hub-and-spoke
topology.
RTB(config-if)#ip ospf network point-to-multipoint

RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0
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Point-to-Multipoint Configuration
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Point-to-Multipoint Configuration
 Duplicates LSA packets: Also as in nonbroadcast mode, when
flooding out a nonbroadcast interface in point-to-multipoint mode,
the router must replicate the LSU. The LSU packet is sent to each
of the neighboring routers of the interface, as defined in the
neighbor table.
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Cisco’s Point-to-Multipoint Non-broadcast mode
RTB(config-if)#ip ospf network point-to-multipoint non-
broadcast

RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0
RTB(config-router)#neighbor 3.1.1.1 cost 10
RTB(config-router)#neighbor 3.1.1.3 cost 20
 Cisco extension to RFC-compliant
point-to-multipoint mode
 Must statically define neighbors,
like nonbroadcast mode
 Like point-to-multipoint mode,
DR/BDR not elected
 Used in special cases where
neighbors cannot be automatically
discovered
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Cisco’s Broadcast Mode
 Makes a WAN interface
appear to be a LAN
 One IP subnet
 Uses multicast hellos to
discover neighbors
 DR and BDR elected
 Requires a full mesh.
RTB(config-if)#ip ospf network broadcast

RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0
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 One IP subnet per subinterface pair
 No DR or BDR election
 Used when only two routers need to
form an adjacency on a pair of
interfaces
 Same properties as any physical
point-to-point physical interface
RTB(config)#interface serial 0/0.1
RTB(config-subif)#ip address 3.1.1.2 255.255.255.0
RTB(config-subif)#interface serial 0/0.2
RTB(config-subif)#ip address 4.1.1.2 255.255.255.0

RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0
RTB(config-router)#network 4.1.1.0 0.0.0.255 area 0
Cisco’s Point-to-Point mode
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Using Subinterfaces in OSPF over a Frame
Relay Configuration
 A physical interface can be split into multiple logical
interfaces, called subinterfaces.
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Configuring a Multipoint Subinterface

 OSPF treat like NBMA
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OSPF over NBMA Topology Summary
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OSPF network types
Full/parial mesh
Full/parial mesh
Partial
/
Star
2 router
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Tracking OSPF Adjacencies (No DR election)
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Tracking OSPF Adjacencies (No DR election)
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Tracking OSPF Adjacencies (DR election)
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Tracking OSPF Adjacencies (DR election)
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Tracking OSPF Adjacencies (DR election)
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Activity
 3.5.10 Drag and Drop: OSPF Network Type
Characteristics
–Upon completion of this activity, the student will be able
identify the different characteristics and DR and BDR election
requirements for the different network types.
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Self Check
1. List types of network in OSPF
2. Which types require DR election
3. Which types require neighbor command

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Summary
 Point-to-Multipoint Configuration
 Point-to-Multipoint Nonbroadcast Configuration
 Using Subinterfaces in OSPF over a Frame Relay
Configuration
 Configuring a Point-to-Point Subinterface
 Configuring a Multipoint Subinterface