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Module 4
OSPF Overview and
Configuration
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 1 OSPF Overview and Configuration
Module Objectives

Define OSPF, features, advantages over RIP
 Describe OSPF LSA, format and Types
 Define LSDB, Initial synchronization, database
exchange & reliable flooding
 Describe Routing Calculations, supported network
type & Database Synchronization
 Describe how to build OSPF Networks
 Define the OSPF routing, areas, router types and
virtual Links
 Differentiate DR, BDR, Router Election
 OSPF Configuration and Examples
 Lab Exercises
 Summary
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 2 OSPF Overview and Configuration
Define OSPF

Dynamic Routing Protocol
 Link State Protocol
 Employ a distributed database model
 More efficient than RIP
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 3 OSPF Overview and Configuration
The OSPF Advantage

OSPF is an interior gateway protocol (IGP)
that is more efficient than RIP.






Consumes fewer network resources
Highly scalable
Faster convergence
A more descriptive routing metric
Route load sharing
Greater security
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 4 OSPF Overview and Configuration
Link-state Protocol

Employ a distributed database model.
 Each router advertises a description of its
local environment



interfaces
costs
neighbor information

Uses a single synchronized database for
collecting advertisements (LSDB)
 Routing table is derived from this database
 Utilize a shortest-path first algorithm
 OSPF is a Link-state routing protocol
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 5 OSPF Overview and Configuration
Basic Features of OSPF






Hello Packets
Link State Advertisements (LSA)
Link State Database
Reliable Flooding
Shortest Path First Routing Calculations
Areas and Inter-area Routing
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 6 OSPF Overview and Configuration
OSPF Hello Packet & Neighbor Discover

OSPF Hello packets are sent out all of a
router’s interfaces to advertise itself to
neighbor routers
 A router learns about its neighbors when it
receives neighbor router’s Hello packet
 Hello packets are sent out every 10 seconds
by default
 If subsequent Hello packet is not received
within 40 seconds, neighbor relationship is
terminated
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 7 OSPF Overview and Configuration
OSPF Hello Packets

Will only be recognized by routers attached
to the same subnet with same subnet mask
 Contains information on parameters for


Hello Interval and
Router Dead Interval

This information is used by neighbor routers
to agree on the communication variables
 This allows an occasional lost Hello packet
not to be interpreted as a link down
condition.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 8 OSPF Overview and Configuration
OSPF Hello Packets (cont.)

In a broadcast environment, it contains the
OSPF router IDs of all routers the sender has
heard up to the point of transmission

This reduces overhead of sending multiple
Hellos

Ensure that the OSPF link is bi-directional

NOTE: An OSPF router will not forward data
packets over a unidirectional link.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 9 OSPF Overview and Configuration
Link State Advertisement (LSA)

Each OSPF router is responsible for
describing its local piece of the routing
topology through the transmission of linkstate advertisements.

Every thirty minutes a router will -- even in
the absence of any change, retransmit this
self-originating data in the event it may have
been lost or corrupted in a neighbor router’s
tables.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 10 OSPF Overview and Configuration
OSPF LSA Format
LS Age
Options

All OSPF LSAs start
with a 20-byte
common header

This provides orderly
updating and removal of
LSAs and organization to
the LSDB
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 11 OSPF Overview and Configuration
LSA Format - LS Age
LS Age
Options

Number of seconds since
the LSA was originated
normally 0 - 30 mins.

If LSA reaches 30 minutes,
originating router will
refresh the LSA by flooding
a new instance.

If LSA reaches 1 hour, it is
deleted from the database.
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 12 OSPF Overview and Configuration
LSA Format - LS Type

Classifies the LSA
according to function






Type 1
Type 2
Type 3
Type 4
Type 5
Type 7
LS Age
Options
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 13 OSPF Overview and Configuration
LSA Format - Link State ID

A unique identification
 Used to describe a router
in the OSPF routing
domain
 Depends on the LS Type

LS Age
Options
LS Type
Link State ID
Advertising Router
Type 1, 2, 3, 4, 5 or 7
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 14 OSPF Overview and Configuration
LSA Format - Advertising Router
LS Age
Options

The originating router’s
OSPF router ID

In practice, this is one of
the router’s IP address
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 15 OSPF Overview and Configuration
LSA Format - LS Sequence Number

A linear sequence number
LS Age
Options

Used to compare a new
LSA with an old LSA
LS Type
Link State ID
Advertising Router

The LSA instance having
the larger LS Sequence
Number is considered to
be more recent.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 16 OSPF Overview and Configuration
LS Sequence Number
LS Checksum
Length
LSA Format - LS Checksum
LS Age
Options

Used to detect data
corruption.

Does not include LS
Age field

Derived using Fletcher
checksum algorithm
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 17 OSPF Overview and Configuration
LSA Types
Type Number
Description
1
2
3
4
5
7
Router-LSAs
Network-LSAs
Summary-LSAs (IP network)
Summary-LSAs (ASBR)
AS external-LSAs
NSSA external-LSAs
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 18 OSPF Overview and Configuration
LS Type 1 - Router-LSAs

Generated by each OSPF
router
 It describes the router’s set
of active interfaces, its
associated cost and any
neighbor information
 Link State ID is set to the
router’s OSPF Router ID
 Flooded throughout a
single area only
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 19 OSPF Overview and Configuration
LS Age
Options
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LS Type 2 - Network-LSAs

Generated by OSPF
Designated Routers (DRs)
LS Age
Options

Describes a network
segment - i.e., broadcast
domain along with the IDs
of all currently attached
routers.
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length

Link State ID field lists the
IP interface address of the
DR
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 20 OSPF Overview and Configuration
LS Type 3 - Summary-LSAs (IP Network)

This originate from Area
Border Routers (ABRs)
LS Age
Options
LS Type
Link State ID

Supports hierarchical
routing through the use
of OSPF areas
Advertising Router
LS Sequence Number
LS Checksum

Link State ID field is an
IP network number
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 21 OSPF Overview and Configuration
Length
LS Type 4 - Summary-LSAs (ASBR)

This originate from Area
Border Routers (ABRs)
LS Age
Options
LS Type
Link State ID

Similar to LS Type 3
Advertising Router

Used when destination is
an Autonomous System
Boundary Router (ASBR)
LS Sequence Number
LS Checksum
Length

The Link State ID is the
AS boundary router’s
OSPF Router ID
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 22 OSPF Overview and Configuration
LS Type 5 - AS-external-LSAs
LS Age


Originated by AS boundary
routers and describes
destinations ex-ternal to
the AS.
Link State ID field specify
an IP network number
Options
LS Type
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 23 OSPF Overview and Configuration
LS Type 7 - NSSA external-LSAs

Allows the import of
external routes that
will not be advertised
out of the NSSA
LS Age
Options
LS Type
Link State ID
Advertising Router

NSSA - Not So Stubby
Area
LS Sequence Number
LS Checksum
Length
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 24 OSPF Overview and Configuration
Router LSA Format - Link ID

Router Type
0
Number of Links
Link ID
Link 1


Link Data

Link Type
# TOS Metrics
Metric
Link ID
Link 2,
etc.
Link Data
Link Type
# TOS Metrics
Metric
Originating router’s link
information follows the LSA
header.
There are four Link IDs
determined by Link Type.
Type 1 Neighboring router’s Router ID
Three of this Link ID are
relevant in a broadcast
network
Link
type Description
Link ID
2
Link to transit network Interface address of
Designated Router
3
Link to stub network
IP network number
4
Virtual link
Neighbor Router ID
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 25 OSPF Overview and Configuration
Router LSA Format - Link Data

For transit and Virtual
Links

specifies the IP address
of associated router
interface.
Router Type
Number of Links
Link ID
Link 1
Link Data
Link Type

For stub networks

Specifies the stub
network mask
0
# TOS Metrics
Metric
Link ID
Link 2,
etc.
Link Data
Link Type
# TOS Metrics
Metric
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 26 OSPF Overview and Configuration
Router LSA Format - Metric

Router Type
0
Number of Links

Link ID

Link 1
Link Data
Link Type
# TOS Metrics
Metric
Link ID
Link 2,
etc.
Link Data
Link Type
# TOS Metrics
Metric
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 27 OSPF Overview and Configuration

The cost of using this
router link.
A user-configurable value
from 1 - 65,535
The larger the metric, the
less likely (more
expensive) data will be
routed over that particular
link.
Connections to STUB
networks are allowed to
advertise a metric of zero.
Link-State Database (LSDB)

The collection of all OSPF LSAs received
 Each OSPF router has an identical LSDB
 Gives complete description of the network:



routers
network segments
interconnectivity (how it is interconnected)

LSDBs are exchanged between neighboring
routers soon after routers discover each
other
 Maintained through a procedure called
reliable flooding
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 28 OSPF Overview and Configuration
LSDB Initial Synchronization

When two neighbors first start
communicating, they must synchronize their
databases before forwarding traffic over
their shared link to prevent routing loops
from occurring.
Switch A
Switch B
Summit 4
Summit 4
Synchronize Databases
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 29 OSPF Overview and Configuration
OSPF-specified Database Exchange

Procedure used by the routers to
synchronize their databases once the hello
protocol determines a bi-directional
connection between router neighbors.

During synchronization, the neighbor
routers do three things:



Forward current LSA headers
Compares the header received to the LSDB
Request the full LSA for new or newer headers
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 30 OSPF Overview and Configuration
Example LSDB Initial Synchronization
switch e
Summit 4
switch d
Summit 4
Switches A thru F are
in a stable OSPF
network and have fully
synchronized
databases
Switch A
Summit 4
Switch F
Summit 4
switch c
Summit 4
switch b
Summit 4
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 31 OSPF Overview and Configuration
OSPF is restarted on
Switch F, forcing
database
synchronization with
switch A.
Example LSDB Initial Synchronization
Switch A
Switch F
Summit 4
Summit 4
OSPF Hello
OSPF Hello: I heard Switch
A
Database Description: Sequence = X
Bidirectionality established
Database Exchange sequence number created
Database Description: Sequence = X with 6 LSA headers
(Router LSA, Switch A, 0x80000007) (Router LSA, Switch d, 0x80000021)
(Router LSA, Switch b, 0x800000b2) (Router LSA, Switch e, 0x80000012)
(Router LSA, Switch c, 0x80000003) (Router LSA, Switch F, 0x80000005)
Database Description: Sequence = X+1
LSA header = (router LSA, switch F, 0x80000001)
Database Description: Sequence = X+1
Sequence number incremented, acknowledges previous
exchange pair
empty database description packet used for
acknowledgement
Link State Request Packet for the following LSAs:
(Router LSA, Switch d)
(Router LSA, Switch e)
(Router LSA, Switch F)
(Router LSA, Switch A)
(Router LSA, Switch b)
(Router LSA, Switch c)
Router requests all LSAs not in its local database
Link State Update packet for the following LSAs:
(Router LSA, Switch A, 0x80000007) (Router LSA, Switch d, 0x80000021)
(Router LSA, Switch b, 0x800000b2) (Router LSA, Switch e, 0x80000012)
(Router LSA, Switch c, 0x80000003) (Router LSA, Switch F, 0x80000005)
Link State Update packet, LSA =
(router LSA, switch F, 0x80000006)
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 32 OSPF Overview and Configuration
Updated LSA for switch F with larger sequence number
OSPF Database - Reliable Flooding

LSA Updates are periodically generated by
a router wishing to update a self-originated
LSA because:



The router’s local state may have changed
The router wants to delete one of its selforiginated LSAs
Used to propagate LSA Updates throughout
the routing domain
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 33 OSPF Overview and Configuration
Reliable Flooding - What Happens






A router will generate a Link-state Update
packet containing one or more LSAs
Update is forwarded out all interfaces.
Neighbor router receives the Update and
compares the LSAs with the LSDB
More recent LSAs are installed in LSDB
Acknowledgement is sent back to
originating route
New Link-state Update containing the LSA is
sent out all interfaces except receiving one.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 34 OSPF Overview and Configuration
OSPF Routing Calculations

With router LSDBs synchronized for all
routers in routing domain

The router will use Dijkstra’s Shortest Path First
algorithm


This allows calculation of shortest paths to all
destinations
Routing table is constructed from the
calculations and includes


network destinations
associated costs
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 35 OSPF Overview and Configuration
OSPF Routing Calculations

Every link carries an associated cost.
Switch H
Switch I
Summit 48
Summit 48
Switch E
1
1
Summit 1
1
5
Switch G
2
3
4
8
5
6
Switch J
7
1
Summit 48
Summit 48
1
1
1
5
5
Switch F
Switch D
Summit 48
Switch K
Summit 48
Summit 1
1
2
3
4
8
5
6
1
7
2
2
Switch C
Summit 4
1
1
Switch A
Switch B
Summit 48
Summit 48
3
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 36 OSPF Overview and Configuration
5
OSPF Routing Calculations
Shortest Path First Calculation for Switch "C"
Iteration
Destination Added to
Shortest-Path Tree
Candidate List Destination
(cost, next hops)
1
Switch C
Switch A (1, Switch A)
Switch B (1, Switch B)
Switch D (2, Switch D)
Switch E (2, Switch E)
2
Switch A
Switch B (1, Switch B)
Switch D (2, Switch D)
Switch E (2, Switch E)
3
Switch B
Switch D (2, Switch D)
Switch E (2, Switch E)
Switch D
Switch E (2, Switch E)
Switch I (3, Switch D)
Switch J (3, Switch D)
Switch K (3, Switch D)
4
5
Switch E
6
7
8
9
10
Switch I
Switch J
Switch K
Switch F
Switch G
11
Switch I
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 37 OSPF Overview and Configuration
Switch I (3, Switch D)
Switch J (3, Switch D)
Switch K (3, Switch D)
Switch F (3, Switch E)
Switch G (3, Switch E)
Switch H (3, Switch E)
Empty
OSPF Routing Calculations

Applying Dijkstra’s SPF algorithm, Switch C’s routing table
would incorporate the highlighted links
Switch H
Switch I
Summit 48
Summit 48
Switch E
1
1
Summit 1
1
5
Switch G
2
3
4
8
5
6
Switch J
7
1
Summit 48
Summit 48
1
1
1
5
5
Switch F
Switch D
Summit 48
Switch K
5
Summit 48
Summit 1
1
2
3
4
8
5
6
1
7
2
2
Switch C
Summit 4
1
1
Switch A
Switch B
Summit 48
Summit 48
3
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 38 OSPF Overview and Configuration
Note that Switch A will
never talk directly to
Switch B as long as the
links thru Switch C
remain stable.
OSPF Routing Calculations

Note how changing a link cost affects the route
calculation for the shortest path
Switch H
Switch I
Summit 48
Summit 48
Switch E
1
1
Summit 1
1
5
Switch G
2
3
4
8
5
6
Switch J
7
1
Summit 48
Summit 48
1
5
5
3
Switch F
Switch D
Summit 48
Switch K
Summit 48
Summit 1
1
2
3
4
8
5
6
1
7
2
Communication with
Switch B is no longer
direct, but must routed
thru Switch A.
3
4
Switch C
Summit 4
1
5
Switch A
Switch B
Summit 48
Summit 48
3
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 39 OSPF Overview and Configuration
With this configuration,
Switch C now has two
paths of equal cost to
communicate with
Switch J.
3
OSPF Network Types

Point-to-Point networks


Non-broadcast Multi-access (NBMA)
networks


X.25, ATM
Point-to-Multipoint networks


Serial lines
Frame Relay
Broadcast networks
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 40 OSPF Overview and Configuration
OSPF Network Type - Broadcast Networks

A network with more than two attached
devices
 Has the ability to address a single physical
message to all of the attached devices
(broadcast)
10.1.1.1
10.1.1.3
10.1.1.2
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 41 OSPF Overview and Configuration
10.1.1.5
10.1.1.4
OSPF Network Type - Broadcast Networks


Only network type supported by Extreme switches
Other Network Types are for WAN use
10.1.1.1
10.1.1.3
10.1.1.2
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 42 OSPF Overview and Configuration
10.1.1.5
10.1.1.4
Broadcast Networks Terminology

DR - Designated Router
 BDR - Backup DR
 DR and BDR Election
 Network LSAs
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 43 OSPF Overview and Configuration
Broadcast Networks - Designated Router

Every broadcast network has a Designated
Router (DR) and a Backup Designated
Router (BDR)
 Each router on the network exchanges link
state information only with the DR and BDR.

This information is used to maintain database
synchronization between the DR and neighbor
routers

This reduces the amount of traffic otherwise
consumed by routing protocol traffic
 Only a DR generates a LS Type 2 - NetworkLSAs
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 44 OSPF Overview and Configuration
DR and BDR Election





First OSPF router on an IP subnet always
becomes the DR
Second OSPF router always becomes BDR
If DR or BDR fail, the OSPF router with the
highest Router Priority will replace the BDR
If two OSPF routers have same Router
Priority, then the OSPF Router ID will break
the tie
A Router Priority of 0 will prevent an OSPF
router from ever being elected as DR or BDR
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 45 OSPF Overview and Configuration
Database Synchronization

An OSPF router will send its Link State
Update (LSU) to the DR and BDR


The destination IP address for the LSU will be
multicast address 224.0.0.6 (All DRouters).
The DR will then flood the update to all
OSPF routers

The destination IP address for the LSU will be
multicast address 224.0.0.5 (All OSPFRouters).
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 46 OSPF Overview and Configuration
Representing Broadcast Subnet in LSDB

If an OSPF router included all known routers on
a common subnet in its router-LSA, there would
be n*(n-1) links in the OSPF database.

By using a new LSA type, the Network-LSA, to
represent the broadcast subnet, the number of
links is reduced from n*(n-1) to n*2.

Each network LSA has a link to every routerLSA, and every router-LSA has a link to the
broadcast subnet’s network-LSA.

DR maintains the network-LSA
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 47 OSPF Overview and Configuration
Type 2: Network LSAs
LS Age
Options
LS Type

Created in order to
reduce the number of
links in each router’s
resulting LSDB

Describes the subnet,
all routers on that
network DR identity
Link State ID
Advertising Router
LS Sequence Number
LS Checksum
Length
Network Mask
Attached Router 1
Attached Router 2, etc.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 48 OSPF Overview and Configuration
Type 2: Network LSAs
Router 1
router-LSA
network-LSA
link-state ID
Router 3
router-LSA
Designated
Router-orginated
network-LSA
network-LSA
link-state ID
router-LSA
link-state ID
router-LSA
link-state ID
router-LSA
link-state ID
router-LSA
link-state ID
Router 2
router-LSA
Router 4
router-LSA
network-LSA
link-state ID
network-LSA
link-state ID
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 49 OSPF Overview and Configuration
The network-LSA
helps in database
synchronization,
since a router
having a routerLSA with a link to
the network-LSA
and vice-versa is
known to have a
database
synchronized with
the Designated
Router.
Building OSPF Networks






Hierarchical Routing
OSPF Routing Hierarchy
OSPF Areas
OSPF Types of Routers
Virtual Links
CLI Commands for OSPF Configuration
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 50 OSPF Overview and Configuration
Hierarchical Routing

OSPF implements a two-level
hierarchical routing scheme

Saves router memory consumed
by the routing table

Saves router resources when
computing the routing table

Saves link bandwidth when
distributing routing data
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 51 OSPF Overview and Configuration
OSPF Areas Defined

The OSPF hierarchy is maintained through
the deployment of OSPF areas
 Each OSPF area is identified by a 32-bit
Area ID
 Each area consists of a collection of one or
more network segments interconnected by
routers
 An area has its own LSDB consisting of
router-LSAs and network-LSAs


These LSAs describe area’s topology
Routing with an area is flat.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 52 OSPF Overview and Configuration
Area’s Router-LSA and Network-LSA
Not flooded beyond the area’s borders
 Detailed knowledge of area’s topology is
hidden from all other areas in the parent
Autonomous System.

Summit 48
Summit 48
Summit 48
Summit 48
Summit 1
Summit 1
1
2
3
Summit 4
4
5
6
8
8
7
7
Summit 3
Summit 48
5
4
Summit 3
Summit 3
Summit 48
1
6
3
2
Summit 4
Summit 3
Summit 3
Area A
Summit 48
Summit 3
Summit 48
Area B
Area “A” does not know the internal topology of Area “B” and vice versa .
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 53 OSPF Overview and Configuration
Area Border Router (ABR)

Manages inter-area communication
 Attached to two or more areas, running
multiple copies of the basic algorithm
 Maintain LSDBs for each attached area and
an additional copy for the backbone
 Condense the topological information of
their attached areas into Type 3: SummaryLSAs for distribution to the backbone.

The backbone in turn distributes the information
to the other areas.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 54 OSPF Overview and Configuration
Area Border Router (ABR) cont.
Summit 48

Summit 48
10.5.1.0/24
Summit 1
1
2
3
8
4
5
6
7
10.5.3.0/24
10.5.2.0/24
Summit 4
Summit 3
g
Summit 3
10.5.4.0/24
Summit 48
Summit 48
Summit 3
Aggregate!!!
10.5.0.0/16
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 55 OSPF Overview and Configuration
ABRs can be
configured to
aggregate some or
all of the networks
within its
dependent area
into a single,
summary network
address with a less
discreet network
mask.
Types of OSPF Areas

Normal Area

Area 0 (Backbone)

Stub Areas
 Not-So-Stubby-Areas (NSSA)
 Virtual Links
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 56 OSPF Overview and Configuration
Normal Area

An area which is not a:


Stub area
NSSA

Can be placed anywhere within the OSPF
routing domain
 Support ASBRs
 Support Virtual Links
 Can distribute external routes
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 57 OSPF Overview and Configuration
Area 0 (Backbone)

Is a Normal Area
 Responsible for distributing routing
information between areas
 Consist of



all area border routers
networks not contained in any other area
and their attached routers

Has an Area ID of 0.0.0.0
 Only one backbone area per AS
 All areas are required to attach directly to
the OSPF backbone area
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 58 OSPF Overview and Configuration
Stub Area

For routers with limited resources

reduce memory and computation requirements

The LSDB is kept as small as possible
 External route information is not distributed

Will use default routes to ABRs instead

Does not support ASBRs
 Does not support virtual links
 Appears to lie on the edge of an OSPF
domain (AS) in configuration
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 59 OSPF Overview and Configuration
Not-So-Stubby-Area (NSSA)

Similar to existing OSPF Stub Area with two
additional capabilities


External routes originating from ASBR connected to NSSA can be advertised within
External routes originating from NSSA can be
propagated to other areas, including the
backbone.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 60 OSPF Overview and Configuration
OSPF Defines Three types of Routers

Internal Router (IR)

Has all of its interfaces within the same area

Area Border Router (ABR)
 Autonomous System Boundary Router
(ASBR)
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 61 OSPF Overview and Configuration
OSPF Hierarchical Components
OSPF Router Types Displayed
R1
R2
R3
R6
R7
Internet
Area 1
R9
Area 2
R8
R4
R 10
ABR
ABR
ASBR
R5
ABR
Area 3
Area 3
R 11
R 12
R 13
Autonomous S ystem
*All other routers that are not labeled ASBR or ABR are Internal Routers
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 62 OSPF Overview and Configuration
Virtual Links

Used when a new area is introduced that
does not have a direct physical attachment
to the backbone

Provides a logical path between the ABR of
the disconnected area and the backbone

A virtual link is established between two
ABRs that have a common area, with one
ABR connected to the backbone
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 63 OSPF Overview and Configuration
OSPF Configuration Example
Area 0.0.0.1
Normal
E
Internet
Area 0.0.0.4
STUB
E
BGP
E
E
E
E
VL
Area 0.0.0.2
Normal
E
Area 0.0.0.0
E
Area 0.0.0.3
Normal
VL
E
RIP
Cloud
Area 0.0.0.5
NSSA
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 64 OSPF Overview and Configuration
Configuring OSPF

Must have a unique router ID for each switch

Recommend manually setting the router ID
of the switches participating in OSPF



Simplifies router management
Prevents corruption of virtual links
Do not use 0.0.0.0 as a router ID
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 65 OSPF Overview and Configuration
OSPF CLI Commands






enable/disable ospf
config ospf add/delete vlan
create/delete ospf area
config ospf vlan area
show ospf area
show ospf interfaces
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 66 OSPF Overview and Configuration
CLI Command - enable/disable ospf
enable ospf
disable ospf
Enable or disable OSPF for the whole router.
Default is disabled.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 67 OSPF Overview and Configuration
CLI Command - config ospf add/del vlan
config ospf add vlan [<name> | all]
config ospf delete vlan [<name> | all]


Enables or disables OSPF on one or all VLANs
(router interfaces).
The default setting is disabled.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 68 OSPF Overview and Configuration
CLI Command - create/del ospf area
create ospf area <areaid>
delete ospf area [<areaid> | all]


Create or delete an OSPF area. Area 0.0.0.0
does not need to be created. It exists by default.
It also cannot be deleted.
Once an OSPF area is removed, the associated
OSPF area and OSPF interface information will
also be removed.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 69 OSPF Overview and Configuration
CLI Command - config ospf vlan area
config ospf vlan <name> area <areaid>


Associates a VLAN (router interface) with/from
an OSPF area. The area must already be
defined. All router interfaces must have an
associated OSPF area.
By default, all router interfaces are associated
with area 0.0.0.0 (backbone).
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 70 OSPF Overview and Configuration
CLI Command - show ospf
show ospf

Displays global OSPF information.
show ospf area {<areaid>}

Displays information about a particular OSPF
area, or all OSPF areas.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 71 OSPF Overview and Configuration
Example: show ospf area
OSPF_Switch4:
show ospf area
Area: 0.0.0.0 Stub: FALSE Rtr Id: 20.20.20.20
Spf Runs: 48 Num ABR: 6 Num ASBR: 0 Num LSA: 43 LSA Chksum:0x170863
Interfaces:
IP addr
Ospf State DR IP addr
BDR IP addr
10.0.2.1
/24 E DOWN 0.0.0.0
0.0.0.0
10.0.1.1
/24 E BDR
10.0.1.2
10.0.1.1
Inter-Area route Filter: None
External route Filter: None
Configured Address Ranges:
Area: 10.11.0.0 Stub: FALSE Rtr Id: 20.20.20.20
Spf Runs: 21 Num ABR: 2 Num ASBR: 0 Num LSA: 35 LSA Chksum:0x16c3de
Interfaces:
IP addr
Ospf State DR IP addr
BDR IP addr
10.11.1.1
/24 E DR
10.11.1.1
10.11.1.2
Inter-Area route Filter: None
External route Filter: None
Configured Address Ranges:
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 72 OSPF Overview and Configuration
CLI Command - show ospf interfaces
show ospf interfaces {vlan <name> | area <areaid>|all}
Displays information about one or all OSPF area, or all
OSPF areas.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 73 OSPF Overview and Configuration
Example: show ospf interface
Summit4: sh
ospf interface
Interface(rif4): 10.15.1.1/24 Vlan: norm151 Ospf: ENABLED Router: ENABLED
AreaId: 10.15.0.0 RtId: 20.20.20.20 Cost: 1 Pri: 1 Transit Delay: 1
Hello Interval: 10s Rtr Dead Time: 40s Retransmit Interval: 5s
Authentication: NONE
State: BDR Number of events: 1
DR RtId: 30.30.30.30 DR IP addr: 10.15.1.3 BDR IP addr: 10.15.1.1
Neighbours:
RtrId: 10.10.10.10 IpAddr: 10.15.1.2 Pri: 1
State: FULL Dr: 10.15.1.3 BDR: 10.15.1.1 Dead Time: 7
RtrId: 30.30.30.30 IpAddr: 10.15.1.3 Pri: 1
State: FULL Dr: 10.15.1.3 BDR: 10.15.1.1 Dead Time: 6
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 74 OSPF Overview and Configuration
Laboratory Exercise

Lab4 - OSPF Configuration I
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 75 OSPF Overview and Configuration
Lab4 - Network Topology
Port 21 Port 18
OSPF_LAB_3
OSPF_LAB_1
.2
Normal
10.13.0.0
.1
NORM131
10.13.1.0/24
OSPF_LAB_3
NORM131 NORM111
OSPF_LAB_1
.2
OSPF_LAB_2
Normal
10.11.0.0
.1
NORM111
10.11.1.0/24
Port 18
Port 21
NORM131
NORM111
OSPF_LAB_2
Port 19
.1
BBONE1
Backbone
0.0.0.0
BBONE1
10.0.1.0/24
Port 19
.2
Normal
10.19.0.0
.1
NORM171
10.19.1.0/24
.2
OSPF_LAB_6
OSPF_LAB_5
BBONE1
Normal
10.17.0.0
.1
NORM151
10.17.1.0/24
OSPF_LAB_5
Port 18
Port 21
NORM191
NORM171
.2
OSPF_LAB_4
OSPF_LAB_6
Port 21 Port 18
NORM191 NORM171
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 76 OSPF Overview and Configuration
OSPF_LAB_4
More OSPF Configuration

config ospf add virtual-link
 config ospf delete virtual-link
 show ospf virtual-link
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 77 OSPF Overview and Configuration
CLI Command - config ospf add virtual-link
config ospf add virtual-link <routerid> <areaid>
config ospf delete virtual-link <routerid> <areaid>


Adds or deletes a virtual link connected to another
area border router (ABR).
Specify the following:


routerid -- Far-end router ID.
Areaid -- Transit area used for connecting the
two end-points. The transit area cannot be the
backbone (0.0.0.0).
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 78 OSPF Overview and Configuration
CLI Command - show ospf virtual-link
show ospf virtual-link {<areaid><routerid> | all}
Displays virtual link information about a particular
router or all routers. Default is all. Contains:
 Area ID and neighbor router ID
 Receive interval, transit delay, Hello interval, and
dead interval.
 Authentication configuration
 Virtual link type and number of events
 Neighbor router ID, IP address, and priority
 Link state, DR ID, BDR ID, and dead time
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 79 OSPF Overview and Configuration
Example: show ospf virtual-link
OSPF_LAB_2:19 # show ospf virtual-link
AreaId: 10.15.0.0 NbrRouterId: 10.10.10.10
Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40
Auth Type: NONE
State: P2P Number of Events: 3
RtrId: 10.10.10.10 IpAddr: 10.15.1.2 Pri: 1
State: FULL Dr: 0.0.0.0 BDR: 0.0.0.0 Dead Time: 9
AreaId: 10.15.0.0 NbrRouterId: 30.30.30.30
Rxmit Interval: 5 Transit Delay: 1 Hello Interval: 10 Dead Interval: 40
Auth Type: NONE
State: P2P Number of Events: 1
RtrId: 30.30.30.30 IpAddr: 10.15.1.3 Pri: 1
State: FULL Dr: 0.0.0.0 BDR: 0.0.0.0 Dead Time: 7
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 80 OSPF Overview and Configuration
Laboratory Exercise

Lab5 - OSPF Configuration II
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 81 OSPF Overview and Configuration
Lab5 - Network Topology 1
Network
OSPF_LAB_3
.3
.2
Normal
10.15.0.0 .2
NORM151
10.15.1.0/24
Physical
Port 21 Port 18
OSPF_LAB_1
.2
OSPF_LAB_3
Normal
10.13.0.0
.1
NORM131
10.13.1.0/24
OSPF_LAB_2
.1
OSPF_LAB_1
Port 22
Port 17
NORM151
.1
NORM121 NORM121
Normal
10.11.0.0
NORM111
10.11.1.0/24
Port 17
Port 18
Port 21
NORM121
NORM121
OSPF_LAB_2
NORM151
NORM151
Port 22
NORM151
Port 19
.1
BBONE1
Backbone
0.0.0.0
BBONE1
10.0.1.0/24
Port 19
.2
Normal
10.19.0.0
.1
NORM191
10.19.1.0/24
BBONE1
OSPF_LAB_5
.1
.2
OSPF_LAB_6
Normal
10.17.0.0
.1
NORM171
10.17.1.0/24
.2
.3
Normal
10.21.0.0
NORM211
10.21.1.0/24
.2
OSPF_LAB_4
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 82 OSPF Overview and Configuration
Port 17
NORM211
Port 22
Port 22
OSPF_LAB_5
Port 18
Port 21
NORM171
NORM171
NORM211
OSPF_LAB_6
NORM211
Port 17
NORM211
Port 21 Port 18
NORM171 NORM171
OSPF_LAB_4
Lab5 - Network Topology 2
Network
Physical
Virtual Links
OSPF_LAB_3
.3
Normal
10.15.0.0 .2
Port 21 Port 18
OSPF_LAB_1
NORM151
10.15.1.0/24
.2
.2
OSPF_LAB_3
NORM131
10.13.1.0/24
.1
.1
OSPF_LAB_2
.1
OSPF_LAB_1
Port 22
Port 17
NORM151
Normal
10.13.0.0
NORM121 NORM121
Normal
10.11.0.0
NORM111
10.11.1.0/24
Port 17
Port 18
Port 21
NORM121
NORM121
OSPF_LAB_2
NORM151
NORM151
Port 22
NORM151
Port 19
.1
BBONE1
Backbone
0.0.0.0
BBONE1
10.0.1.0/24
Port 19
.2
Normal
10.19.0.0
NORM191
10.19.1.0/24
.1
BBONE1
OSPF_LAB_5
.1
.2
OSPF_LAB_6
.1
.3
NORM211
10.21.1.0/24
.2
NORM211
NORM171
10.17.1.0/24
.2
Normal
10.21.0.0
Port 17
Normal
10.17.0.0
OSPF_LAB_4
Virtual Links
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 83 OSPF Overview and Configuration
Port 22
Port 22
OSPF_LAB_5
Port 18
Port 21
NORM171
NORM171
NORM211
OSPF_LAB_6
NORM211
Port 17
NORM211
Port 21 Port 18
NORM171 NORM171
OSPF_LAB_4
More OSPF Configuration - Areas

config ospf area normal
 config ospf area stub
 config ospf area nssa
 show ospf
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 84 OSPF Overview and Configuration
CLI Command - config ospf area normal
config ospf area <areaid> normal



Configure an OSPF area as a normal area
Default area type is normal
Area 0.0.0.0 can only be normal
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 85 OSPF Overview and Configuration
CLI Command - config ospf area stub
config ospf area <areaid> stub
[summary|nosummary] stub-default-cost <cost>


Configures an OSPF area as a stub area.
Stub-default-cost is the the cost of the default
summary-LSA that the router should advertise into the
area
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 86 OSPF Overview and Configuration
CLI Command - config ospf area nssa
config ospf area <areaid> nssa
[summary|nosummary] stub-default-cost
<cost> {translate}



Configures an OSPF area as a NSSA.
Stub-default-cost is the the cost of the default
summary-LSA that the router should advertise
into the area
Translate option: determines whether type 7
LSAs are translated into type 5 LSAs.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 87 OSPF Overview and Configuration
CLI Command - show ospf
show ospf
Display global OSPF information:









Router ID
OSPF state
Is router an autonomous system boundary router (Y/N)?
Is router an area border router (Y/N)?
Number of external LSAs processed
External LSA checksum
Number of originating new LSAs
Number of received new LSAs
Shortest Path First hold time
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 88 OSPF Overview and Configuration
Example: show ospf
Summit4: show ospf
Router Id
OSPF ASBR ABR ExtLSA ExtLSACsum OrigNewLSA RxNewLSA
SpfHoldTime
20.20.20.20 E
NO YES
0
0x0
14694
20634
RouterId Selection: User Configured Export Static: Disabled
Export Static: Disabled
Export Rip: Disabled
ASBR route Filter: None
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 89 OSPF Overview and Configuration
3
Laboratory Exercise

OSPF Lab6
 Utilizing the CLI Commands:



config ospf area normal
config ospf area stub
show ospf
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 90 OSPF Overview and Configuration
Lab6 - Network Topology
Virtual Links
Stub
10.14.0.0
STUB141
10.14.1.1/24
STUB142
10.14.2.1/24
STUB143
10.14.3.1/24
STUB144
10.14.4.1/24
Stub
10.12.0.0
STUB121
10.12.1.1/24
STUB122
10.12.2.1/24
STUB123
10.12.3.1/24
STUB124
10.14.2.1/24
Normal
10.15.0.0
OSPF_LAB_3
.3
.2
Normal
10.13.0.0
NORM131
10.13.1.0/24
NORM151
10.15.1.0/24
NORM152
10.15.2.0/24
NORM153
10.15.3.0/24
NORM154
10.15.4.0/24
Port1 x-over to Port2
Port 21 Port 18
.2
OSPF_LAB_1
OSPF_LAB_3
.1
OSPF_LAB_1
Port 17
NORM151
OSPF_LAB_2
NORM131 NORM111
Port 22
.2
.1
.1
Port1 x-over to Port2
Normal
10.11.0.0
NORM111
10.11.1.0/24
Port 17
Port 18
Port 21
NORM131
NORM111
OSPF_LAB_2
NORM151
NORM151
Port 22
NORM151
Port 19
.1
BBONE1
Port2 x-over to Port3
Backbone
0.0.0.0
BBONE1
10.0.1.0/24
Port2 x-over to Port3
.2
Normal
10.19.0.0
NORM191
10.19.1.0/24
.1
OSPF_LAB_6
Stub
10.20.0.0
STUB201
10.20.1.1/24
STUB202
10.20.2.1/24
STUB203
10.20.3.1/24
STUB204
10.20.2.1/24
BBONE1
OSPF_LAB_5
.1
Normal
10.21.0.0
.2
.3
NORM211
10.21.1.0/24
NORM212
10.21.2.0/24
NORM213
10.21.3.0/24
NORM214
10.21.4.0/24
Port 19
.1
Virtual Links
NORM211
NORM171
10.17.1.0/24
Port 22
.2
.2
Port 17
Normal
10.17.0.0
Port 22
OSPF_LAB_5
Port 18
Port 21
NORM191
NORM171
NORM211
OSPF_LAB_4
OSPF_LAB_6
NORM211
Port 17
NORM211
Port 21 Port 18
OSPF_LAB_4
NORM191 NORM171
Stub
10.18.0.0
STUB181
10.18.1.1/24
STUB182
10.18.2.1/24
STUB183
10.18.3.1/24
STUB184
10.18.2.1/24
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 91 OSPF Overview and Configuration
Port1 x-over to Port2
Port1 x-over to Port2
More OSPF Configuration Commands










config ospf routeid
config ospf area add range
config ospf vlan area cost
config ospf vlan area priority
*enable iproute sharing
enable/disable ospf exportstatic type
config ospf vlan area virtual link authentication
config ospf vlan area virtual link timer
config ospf spf-hold-time
show ospf lsdb
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 92 OSPF Overview and Configuration
CLI Command - config ospf area add range
config ospf area <areaid> add range
<ipaddress> <mask> [advertise | noadvertise]
{type 3|type 7}
config ospf area <areaid> delete range
<ipaddress> <mask>


Configures or deletes a range of IP addresses in an
OSPF area.
On add, and if advertised, the range is exported as a
single LSA by the ABR.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 93 OSPF Overview and Configuration
CLI Command - config ospf … cost
config ospf [vlan <name> | area <areaid> | all]
cost <number>



Configures the cost (metric) of one or all
interface(s).
The default cost of an interface is 1.
The maximum cost is 65,535.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 94 OSPF Overview and Configuration
CLI Command - config ospf … priority
config ospf [vlan <name> | area <areaid> | all]
priority <number>




Configures the priority used in the designated
router-election algorithm for one or all IP
interface(s) or for all the interfaces within the
area.
The range is 0 - 255
The Default priority setting is 1
A value of 0 disqualifies the router from election
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 95 OSPF Overview and Configuration
CLI Command - enable iproute sharing
enable iproute sharing



Enables load sharing if multiple routes to the
same destination are available (equal cost
multipath)
Only paths with the same lowest cost are
shared.
The default setting is disabled.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 96 OSPF Overview and Configuration
CLI Command - enable/disable ospf exportstatic
enable ospf export static cost {<metric>}
[ase-type-1|ase-type-2] {tag <number>}
disable ospf export static



Enable/disables the distribution of static routes
into the OSPF domain.
The default tag number is 0.
The default setting is disabled.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 97 OSPF Overview and Configuration
CLI Command - config ospf … authentication
config ospf [vlan <name> | area <areaid> | virtual-link
<routerid> <areaid>] authentication
[simple-password <password> | md5 <md5_key_id>
<md5_key> | none]


Configure OSPF authentication information for one
interface or all the interfaces in an AREA.
When the OSPF AREA ID is specified, then the
authentication information is applied to all the OSPF
interfaces within the area.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 98 OSPF Overview and Configuration
CLI Command - config ospf … timer
config ospf [vlan <name> | area <areaid> | virtuallink <routerid>] timer <retransmission_interval>
<transmission_delay> <hello_interval>
<dead_interval>


Configures the timers for one interface or all the
interfaces in the same OSPF area.
The following default, min, and max values (in seconds) are used:
Variable
RETRANSMISSION
DELAY
HELLO
DEAD INTERVAL
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 99 OSPF Overview and Configuration
Default Min
5
0
1
0
10
1
40
1
Max
3600
3600
65535
2147483647
CLI Command - config ospf spf-hold-time
config ospf spf-hold-time {<seconds>}


Configures the minimum number of seconds
between Shortest Path First (SPF) recalculations.
The default setting is 3 seconds.
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 100 OSPF Overview and Configuration
CLI Command - show ospf lsdb
show ospf lsdb {detail} area [<areaid> | all]
[router | network | summary-net |
summary-asb | as_external | external-type 7 | all}




Displays a table of the current LSDB.
The user can filter the display using either area ID,
the remote router's router ID, or the link state ID.
Default is all with no detail.
If detail is specified, each entry includes complete
LSA information
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 101 OSPF Overview and Configuration
Example: show ospf lsdb
OSPF_LAB_2:18 # show
ospf lsdb area all all
Router LSAs for area 0.0.0.0
Link State ID Adv Router
Seq#
Age Chksum #Links
------------------------------------------------------------10.10.10.10 10.10.10.10 0x8000011d 1227 0xafc6 1
20.20.20.20 20.20.20.20 0x80006754 510 0x835f 3
30.30.30.30 30.30.30.30 0x800040a9 1245 0xf018 1
40.40.40.40 40.40.40.40 0x80000169 450 0x6e4c 1
50.50.50.50 50.50.50.50 0x800001ab 1279 0x7f83 3
60.60.60.60 60.60.60.60 0x8000016c 461 0x8095 1
Network LSAs for area 0.0.0.0
Link State ID Adv Router
Seq#
Age Chksum
------------------------------------------------------------10.0.1.2
50.50.50.50 0x80000169 1273 0xb14f
Summary LSAs for area 0.0.0.0
Link State ID Adv Router
Seq#
Age Chksum
------------------------------------------------------------10.11.1.0
10.10.10.10 0x80000114 1230 0x dfc
10.11.1.0
20.20.20.20 0x8000011b 1250 0xd109
10.12.0.0
10.10.10.10 0x80000109 1018 0x22f2
10.13.1.0
20.20.20.20 0x80000194 1250 0xc698
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 102 OSPF Overview and Configuration
Laboratory Exercise

OSPF Lab7
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 103 OSPF Overview and Configuration
Lab7 - Network Topology
Network
Physical
Virtual Links
Stub
10.14.0.0
Summarize
to
10.14.0.0/16
STUB141
10.14.1.1/24
STUB142
10.14.2.1/24
STUB143
10.14.3.1/24
STUB144
10.14.4.1/24
Stub
10.12.0.0
Summarize
to
10.12.0.0/16
STUB121
10.12.1.1/24
STUB122
10.12.2.1/24
STUB123
10.12.3.1/24
STUB124
10.14.2.1/24
Normal
10.15.0.0
OSPF_LAB_3
.3
.2
Normal
10.13.0.0
NORM131
10.13.1.0/24
NORM151
10.15.1.0/24
NORM152
10.15.2.0/24
NORM153
10.15.3.0/24
NORM154
10.15.4.0/24
Summarize
.2
to OSPF_LAB_1
10.15.0.0/16
Port1 x-over to Port2
Port 21 Port 18
OSPF_LAB_3
.1
OSPF_LAB_1
Port 17
NORM151
OSPF_LAB_2
NORM131 NORM111
Port 22
.2
.1
.1
Port1 x-over to Port2
Normal
10.11.0.0
NORM111
10.11.1.0/24
Port 17
Port 18
Port 21
NORM131
NORM111
OSPF_LAB_2
Port 22
NORM151
.1
NORM151
NORM151
Port 19
Port 20
BBONE1
BBONE2
Port 19
Port 20
BBONE1
BBONE2
Port2 x-over to Port3
Backbone
0.0.0.0
BBONE1
10.0.1.0/24
BBONE2
10.0.2.0/24
Equal-Cost Multipath
Port2 x-over to Port3
.2
Normal
10.19.0.0
NORM191
10.19.1.0/24
.1
OSPF_LAB_5
.1
Normal
10.21.0.0
.2
OSPF_LAB_6
Stub
10.20.0.0
STUB201
10.20.1.1/24
STUB202
10.20.2.1/24
STUB203
10.20.3.1/24
STUB204
10.20.2.1/24
Summarize
to
10.21.0.0/16
Summarize
to
10.20.0.0/16
.3
NORM211
10.21.1.0/24
NORM212
10.21.2.0/24
NORM213
10.21.3.0/24
NORM214
10.21.4.0/24
.1
Virtual Links
NORM211
NORM171
10.17.1.0/24
Port 22
.2
.2
Port 17
Normal
10.17.0.0
Port 22
OSPF_LAB_5
Port 18
Port 21
NORM191
NORM171
NORM211
OSPF_LAB_4
OSPF_LAB_6
NORM211
Port 17
NORM211
Port 21 Port 18
OSPF_LAB_4
NORM191 NORM171
Stub
10.18.0.0
Summarize
to
10.18.0.0/16
STUB181
10.18.1.1/24
STUB182
10.18.2.1/24
STUB183
10.18.3.1/24
STUB184
10.18.2.1/24
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 104 OSPF Overview and Configuration
Port1 x-over to Port2
Port1 x-over to Port2
Summary









Define OSPF, features, advantages over RIP
Describe OSPF LSA, format and Types
Define LSDB, Initial synchronization,
database exchange & reliable flooding
Describe Routing Calculations, supported
network type & Database Synchronization
Describe how to build OSPF Networks
Define the OSPF routing, areas, router types
and virtual Links
Differentiate DR, BDR, Router Election
OSPF Configuration and Examples
Lab Exercises
LE-201 - Unicast Routing and L3 Switch Configuration
Module 4 - 105 OSPF Overview and Configuration