This document provides an overview of OSPF configuration and features. It describes how to configure multiple OSPF areas on routers and validate the routing tables. Key aspects covered include OSPF packet types, basic features like route updates and ECMP support, defining areas, router types, configuring networks on interfaces in different areas, and using commands to display neighbor relationships and routing tables. The goal is to help readers understand how to set up an OSPF routing domain with multiple areas.

1. OSPF Initial
Configuration
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2. Contents
1. OSPF Features and Configuration
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3. OSPF Protocol Introduction
OSPF (open shortest path first) is an IGP (interior gateway protocol)
routing protocol and it is based on link state algorithm.
OSPF runs on IP layer directly and the value of IP protocol field is 89
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OSPF Packet Types
OSPF Protocol
Header
Frame
Checksu
m
OSPF Protocol
Packet
IP Packet
Header
Link
Layer
Header
IP protocol value is 89

4. OSPF Basic Features
Supporting classless inter-domain routing (CIDR)
Dividing the whole routing domain into different areas
Loop-free
Fast route update and convergence
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Fast route update and convergence
Using IP multicast address to send and receive protocol
message
Supporting ECMP (equal cost multi-path)
Supporting authentication

5. OSPF Multiple Areas
Area 0
Area 1
Area 4
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Area 2
Area 3
Area 0 is backbone area,
all the ABRs have one
interface belongs to Area
0 at least.

6. Type of Router
ABR
BR
Area 0
Area 1
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IR ASBR
Area 1
Area 2
AS100
AS200
OSPF
RIP

7. OSPF Multiple Area Configuration
Area 0
RTC
RTB
[RTB]router id 2.2.2.2
[RTB]ospf
[RTB-ospf-1]area 1
[RTB-ospf-1-area-0.0.0.1]network 2.2.2.2 0.0.0.0
[RTB-ospf-1-area-0.0.0.1]network 10.1.1.0 0.0.0.255
[RTB-ospf-1-area-0.0.0.1]quit
[RTB-ospf-1]area 0
[RTB-ospf-1-area-0.0.0.0]network 10.1.2.0 0.0.0.255
[RTB-ospf-1-area-0.0.0.0]return
<RTB>
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Area 0
Area 1 Area 2
RTA
Loopback0
RTC
RTD
2.2.2.2/32
Loopback0
1.1.1.1/32
RTB
E0/0
10.1.1.0/24
E0/0
.2
.1
Loopback0
3.3.3.3/32
Loopback0
4.4.4.4/32
E0/1
10.1.2.0/24
.1 .2
E0/0
E0/1
E0/0
10.1.3.0/24
.1
.2

8. OSPF Multiple Area Configuration
Area 0 RTC
RTB
[RTC]router id 3.3.3.3
[RTC]ospf
[RTC-ospf-1]area 0
[RTC-ospf-1-area-0.0.0.0]network 10.1.2.0 0.0.0.255
[RTC-ospf-1-area-0.0.0.0]quit
[RTC-ospf-1]area 2
[RTC-ospf-1-area-0.0.0.2]network 3.3.3.3 0.0.0.0
[RTC-ospf-1-area-0.0.0.2]network 10.1.3.0 0.0.0.255
[RTC-ospf-1-area-0.0.0.2]return
<RTC>
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Area 0
Area 1 Area 2
RTA
Loopback0
RTC
RTD
2.2.2.2/32
Loopback0
1.1.1.1/32
RTB
E0/0
10.1.1.0/24
E0/0
.2
.1
Loopback0
3.3.3.3/32
Loopback0
4.4.4.4/32
E0/1
10.1.2.0/24
.1 .2
E0/0
E0/1
E0/0
10.1.3.0/24
.1
.2

9. OSPF Multiple Area Configuration
Area 0
Area 1 Area 2
Loopback0
RTC
2.2.2.2/32
RTB
10.1.1.0/24
E0/0
.2
Loopback0
3.3.3.3/32
E0/1
10.1.2.0/24
.1 .2
E0/0
E0/1
10.1.3.0/24
.1
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RTA RTD
Loopback0
1.1.1.1/32
E0/0
10.1.1.0/24
.1
Loopback0
4.4.4.4/32
E0/0
10.1.3.0/24
.2
[RTD]router id 4.4.4.4
[RTD]ospf
[RTD-ospf-1]area 2
[RTD-ospf-1-area-0.0.0.2]network 4.4.4.4 0.0.0.0
[RTD-ospf-1-area-0.0.0.2]network 10.1.3.0 0.0.0.255
[RTD-ospf-1-area-0.0.0.2]return
<RTD>

10. Display Neighbor Relationship
[RTB]display ospf peer
OSPF Process 1 with Router ID 2.2.2.2
Neighbors
Area 0.0.0.0 interface 10.1.2.1(Ethernet0/1)’s neighbor（
（
（
（s）
）
）
）
Router ID: 3.3.3.3 Address: 10.1.2.2 GR State: Normal
State: Full Mode:Nbr is Master Priority: 1
DR: 10.1.2.1 BDR: 10.1.2.2
Router ID
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DR: 10.1.2.1 BDR: 10.1.2.2
Dead timer due in 33 sec
Neighbor is up for 00:00:17
Neighbors
Area 0.0.0.1 interface 10.1.1.2(Ethernet0/1)’s neighbor（
（
（
（s）
）
）
）
Router ID: 1.1.1.1 Address: 10.1.1.1 GR State: Normal
State: Full Mode:Nbr is Slave Priority: 1
DR: 10.1.1.1 BDR: 10.1.1.2
Dead timer due in 35 sec
Neighbor is up for 00:00:27
Neighbor information of
area 0
Neighbor
information of area 0

11. Validating Routing Table
[RTD]display ip routing-table
Routing Table: public net
Destination/Mask Protocol Pre Cost Nexthop Interface
1.1.1.1/32 OSPF 10 4 10.1.3.1 Ethernet0/0
2.2.2.2/32 OSPF 10 3 10.1.3.1 Ethernet0/0
3.3.3.3/32 OSPF 10 2 10.1.3.1 Ethernet0/0
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4.4.4.4/32 DIRECT 0 0 127.0.0.1 InLoopBack0
10.1.1.0/24 OSPF 10 3 10.1.3.1 Ethernet0/0
10.1.2.0/24 OSPF 10 2 10.1.3.1 Ethernet0/0
10.1.3.0/24 DIRECT 0 0 10.1.3.2 Ethernet0/0
10.1.3.2/32 DIRECT 0 0 127.0.0.1 InLoopBack0
127.0.0.0/8 DIRECT 0 0 127.0.0.1 InLoopBack0
127.0.0.1/32 DIRECT 0 0 127.0.0.1 InLoopBack0

12. Thank you
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