- Open Shortest Path First (OSPF) is an open standard link-state routing protocol that works with link state advertisements to dynamically calculate the shortest path to destinations. It maintains neighbor, database, and routing tables. - OSPF uses areas and link state routing to converge quickly and find the shortest paths between routers within an autonomous system. It supports hierarchical routing designs and classless routing.

1. 1

2. Open Shortest Path First
• Open standard protocol
• Successor of RIP
• Classless routing protocol
• Works with Link State Advertisements
• Updates are through Multicast (224.0.0.5 )
• Administrative distance is 110
• Metric = Cost =108/Bandwidth in bps (CISCO)
2

3. OSPF (contd..)
• Hello packets are sent every 10 seconds
• Faster Convergence
• Hierarchical design with Multiple Areas
• Area 0 is called the backbone area
• Router ID
The highest IP address of the active physical interface
of the router is Router ID.
If logical interface is configured, the highest IP
address of the logical interface is Router ID
3

4. OSPF Tables
• It maintains three tables :
Neighbor Table
Neighbor table contains information about the directly
connected ospf neighbors forming adjacency.
Database table
Database table contains information about the entire
view of the topology with respect to each router.
Routing information Table
Routing table contains information about the best path
calculated by the shortest path first algorithm in the
database table.
4

5. OSPF - Network Diagram
AREA 0
10.0.0.1/8
S0
HYD
11.0.0.1/8
S0
S1
10.0.0.2/8
E0
192.168.1.150/24
LAN - 192.168.1.0/24
CHE
S1
11.0.0.2/8
E0
192.168.2.150/24
LAN - 192.168.2.0/24
BAN
E0
192.168.3.150
LAN - 192.168.3.0/24
5

6. Disadvantages of OSPF
• Consumes More Memory and CPU processing
6

7. 7

8. Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-2000 Microsoft Corp.
C:> telnet 192.168.1.150
Connecting .....
================================
Welcome to Hyderabad Router
================================
User Access Verification
password : ****
Directly Connected Networks on
Directly Connected Networks on
Hyderabad> enable
HYDERABAD Router
password : ****
HYDERABAD Router
Hyderabad# configure terminal
192.168.1.0
192.168.1.0
Enter configuration commands, one per line. End with CNTL/Z.
10.0.0.0
10.0.0.0
Hyderabad(config)# interface serial 0
Hyderabad(config-if)# ip address 10.0.0.1 255.0.0.0
Hyderabad(config-if)# no shut
Hyderabad(config-if)# clockrate 64000
Hyderabad(config-if)# encapsulation hdlc
Hyderabad(config-if)# exit
Hyderabad(config)#
8

9. Hyderabad(config)# no ip routing
Hyderabad(config)# ip routing
Hyderabad(config)# router ospf 1
Hyderabad(config-router)# network 192.168.1.0 0.0.0.255 area 0
Hyderabad(config-router)# network 10.0.0.0 0.255.255.255 area 0
Hyderabad(config-router)# Configuring OSPF
Configuring OSPF
Router(config)# router ospf <pid>
Router(config)# router ospf <pid>
Router(config-router)# network <Network ID>
Router(config-router)# network <Network ID>
<wildcard mask> area <area id>
<wildcard mask> area <area id>
9

10. Hyderabad(config)# no ip routing
Hyderabad(config)# ip routing
Hyderabad(config)# router ospf 1
Hyderabad(config-router)# network 192.168.1.0 0.0.0.255 area 0
Hyderabad(config-router)# network 10.0.0.0 0.255.255.255 area 0
Hyderabad(config-router)# ^Z
Hyderabad# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i- IS-IS, L1-IS-IS level-1, L2-IS-IS level-2,*- candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
C
10.0.0.0/8 is directly connected, Serial0
O
11.0.0.0/8 [110/128] via 10.0.0.2, 00:00:36, Serial0
C
192.168.1.0/24 is directly connected, Ethernet0
O
192.168.2.0/24 [110/74] via ofOSPF
Metric 10.0.0.2, 00:00:36, Serial0
110 isMetricof but
110 isnothing OSPF
nothing but
O – for OSPF routes
O – for OSPF routes
Administrative Distance
O
192.168.3.0/24 [110/138] via 10.0.0.2, 00:00:36, Serial0
Cost
Administrative Distance
Cost
Hyderabad#
10

11. Hyderabad# show ip ospf database
OSPF Router with ID (192.168.1.150) (Process ID 1)
Router Link States (Area 0)
Link ID
192.168.1.150
192.168.2.150
192.168.3.150
ADV Router
192.168.1.150
192.168.2.150
192.168.3.150
Age
790
234
232
Seq#
0x80000003
0x80000005
0x80000003
Checksum
0x897B
0x542
0xD328
Hyderabad# show ip ospf neighbor
Neighbor ID
192.168.2.150
Hyderabad#
Pri
1
State
FULL/
-
Dead Time
00:00:36
Address
10.0.0.2
11
Link
3
5
3

12. Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-2000 Microsoft Corp.
C:> telnet 192.168.2.150
Connecting .....
================================
Welcome to Chennai Router
================================
User Access Verification
password : ****
Directly Connected Networks on
Chennai> enable Directly Connected Networks on
CHENNAI Router
password : ****
CHENNAI Router
Chennai# configure terminal
192.168.2.0
192.168.2.0
Enter configuration commands, one per line. End with CNTL/Z.
10.0.0.0
10.0.0.0
Chennai(config)# interface serial 1
11.0.0.0
11.0.0.0
Chennai(config-if)# ip address 10.0.0.2 255.0.0.0
Chennai(config-if)# no shut
Chennai(config-if)# encapsulation hdlc
Chennai(config-if)# interface serial 0
Chennai(config-if)# ip address 11.0.0.1 255.0.0.0
Chennai(config-if)# no shut
Chennai(config-if)# encapsulation hdlc
12

13. Chennai(config)# no ip routing
Chennai(config)# ip routing
Chennai(config)# router ospf 2
Chennai(config-router)# network 192.168.2.0 0.0.0.255 area 0
Chennai(config-router)# network 10.0.0.0 0.255.255.255 area 0
Chennai(config-router)# network 11.0.0.0 0.255.255.255 area 0
Configuring OSPF
Configuring OSPF
Chennai(config-router)#
Router(config)# router ospf <pid>
Router(config)# router ospf <pid>
Router(config-router)# network <Network ID>
Router(config-router)# network <Network ID>
<wildcard mask> area <area id>
<wildcard mask> area <area id>
13

14. Chennai(config)# no ip routing
Chennai(config)# ip routing
Chennai(config)# router ospf 2
Chennai(config-router)# network 192.168.2.0 0.0.0.255 area 0
Chennai(config-router)# network 10.0.0.0 0.255.255.255 area 0
Chennai(config-router)# network 11.0.0.0 0.255.255.255 area 0
Chennai(config-router)# ^Z
Chennai# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i- IS-IS, L1-IS-IS level-1, L2-IS-IS level-2,*- candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
C
10.0.0.0/8 is directly connected, Serial1
C
11.0.0.0/8 is directly connected, Serial0
O
192.168.1.0/24 [110/74] via 10.0.0.1, 00:01:33, Serial1
C
192.168.2.0/24 is directly connected, Ethernet0
O
192.168.3.0/24 [110/74] isMetricof OSPF 00:01:33, Serial0
Metric of OSPF
110 isnothing but
110 via 11.0.0.2,
nothing but
O – for OSPF routes
O – for OSPF routes Administrative Distance
Chennai#
Cost
Administrative Distance
14
Cost

15. Chennai# show ip ospf database
OSPF Router with ID (192.168.2.150) (Process ID 2)
Router Link States (Area 0)
Link ID
ADV Router
192.168.1.150
192.168.1.150
192.168.2.150
192.168.2.150
192.168.3.150
192.168.3.150
Chennai# show ip ospf neighbor
Neighbor ID
192.168.3.150
192.168.1.150
Chennai#
Pri
1
1
State
FULL/
FULL/
-
Age
1253
695
693
Seq#
0x80000003
0x80000005
0x80000003
Dead Time
00:00:35
00:00:32
Checksum
0x897B
0x542
0xD328
Address
11.0.0.2
10.0.0.1
15
Link
3
5
3

16. Microsoft Windows 2000 [Version 5.00.2195]
(C) Copyright 1985-2000 Microsoft Corp.
C:> telnet 192.168.3.150
Connecting .....
================================
Welcome to Banglore Router
================================
User Access Verification
password : ****
Directly Connected Networks on
Banglore> enableDirectly Connected Networks on
Banglore Router
password : ****
Banglore Router
Banglore# configure terminal
192.168.3.0
192.168.3.0
Enter configuration commands, one per line. End with CNTL/Z.
11.0.0.0
11.0.0.0
Banglore(config)# interface serial 1
Banglore(config-if)# ip address 11.0.0.2 255.0.0.0
Banglore(config-if)# no shut
Banglore(config-if)# clockrate 64000
Banglore(config-if)# encapsulation hdlc
Banglore(config-if)# exit
Banglore(config)#
16

17. Banglore(config)# no ip routing
Banglore(config)# ip routing
Banglore(config)# router ospf 1
Banglore(config-router)# network 192.168.3.0 0.0.0.255 area 0
Banglore(config-router)# network 11.0.0.0 0.255.255.255 area 0
Banglore(config-router)#
Configuring OSPF
Configuring OSPF
Router(config)# router ospf <pid>
Router(config)# router ospf <pid>
Router(config-router)# network <Network ID>
Router(config-router)# network <Network ID>
<wildcard mask> area <area id>
<wildcard mask> area <area id>
17

18. Banglore(config)# no ip routing
Banglore(config)# ip routing
Banglore(config)# router ospf 1
Banglore(config-router)# network 192.168.3.0 0.0.0.255 area 0
Banglore(config-router)# network 11.0.0.0 0.255.255.255 area 0
Banglore(config-router)# ^Z
Banglore# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i- IS-IS, L1-IS-IS level-1, L2-IS-IS level-2,*- candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
O
10.0.0.0/8 [110/128] via 11.0.0.1, 00:02:09, Serial1
C
11.0.0.0/8 is directly connected, Serial1
O
192.168.1.0/24 [110/138] via OSPF
Metric
110 isMetricof 11.0.0.1, 00:02:09, Serial1
nothing but
O –192.168.2.0/24 [110/74] via of OSPF
for OSPF routes 110 is nothing but
O O – for OSPF routes
11.0.0.1,
Administrative Distance
Cost
Administrative Distance 00:02:09, Serial1
Cost
C
192.168.3.0/24 is directly connected, Ethernet0
Banglore#
18

19. Banglore# show ip ospf database
OSPF Router with ID (192.168.3.150) (Process ID 1)
Router Link States (Area 0)
Link ID
192.168.1.150
192.168.2.150
192.168.3.150
ADV Router
192.168.1.150
192.168.2.150
192.168.3.150
Age
1506
948
944
Seq#
0x80000003
0x80000005
0x80000003
Checksum
0x897B
0x542
0xD328
Link
3
5
3
Banglore# show ip ospf neighbor
Neighbor ID
192.168.2.150
Banglore#
Pri
1
State
FULL/
-
Dead Time
00:00:37
Address
11.0.0.10.1
19

20. Hyderabad# ping 192.168.3.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.3.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Hyderabad# ping 192.168.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Hyderabad#
20

21. Chennai# ping 192.168.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Chennai# ping 192.168.3.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.3.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Chennai#
21

22. Banglore# ping 192.168.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Banglore# ping 192.168.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 40/43/44 ms
Banglore#
22