Module 3 - Implementing OSPF in an NBMA Network ppt

The neighbor command optionspriority number Specifies the priority of neighbor.. poll-interval number Amount of time a NBMA interface waits before sending hellos to the neighbor even if

BSCI Module 3 Lesson 5 - Implementing OSPF in

an NBMA Network

 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

Configuring OSPF over Frame Relay

RFC-compliant Non-broadcast Mode

The neighbor command options

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)#

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

The show ip ospf neighbor Command

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 mesh or hub-and-spoke topology.

partial-RTB(config-if)#ip ospf network point-to-multipoint

-RTB(config-router)#network 3.1.1.0 0.0.0.255 area 0

Point-to-Multipoint Configuration

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

Cisco’s Point-to-Multipoint Non-broadcast mode

RTB(config-if)#ip ospf network point-to-multipoint

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

 One IP subnet per subinterface pair

Using Subinterfaces in OSPF over a Frame

Relay Configuration

 A physical interface can be split into multiple logical

interfaces, called subinterfaces

Configuring a Multipoint Subinterface

 OSPF treat like NBMA

OSPF over NBMA Topology Summary

OSPF network types

Full/parial mesh

Full/parial mesh

Partial / Star

2 router

Tracking OSPF Adjacencies (No DR election)

Tracking OSPF Adjacencies (No DR election)

Tracking OSPF Adjacencies (DR election)

Tracking OSPF Adjacencies (DR election)

Tracking OSPF Adjacencies (DR election)

Self Check

1 List types of network in OSPF

2 Which types require DR election

3 Which types require 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

Q and A

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