2. Open Shortest Path First OSPF (Part 2) George Macri E-mail: gmacri@homemail.comgmacri@homemail.com 6 th CEENET Workshop, Budapest 2000

3. Interior IP Routing Protocols Routing Information Protocol (RIP) Interior Gateway Routing Protocol (IGRP) Open Shortest Path First (OSPF) Protocol Enhanced IGRP (EIGRP) Routing Information Protocol (RIP) Interior Gateway Routing Protocol (IGRP) Open Shortest Path First (OSPF) Protocol Enhanced IGRP (EIGRP) Application Transport Internet Network Interface Hardware

4. IP Routing Configuration Tasks Network 172.30.0.0 IGRP, RIP Global configuration Select routing protocol(s) Network 160.89.0.0 Network 172.16.0.0 Specify network(s)

5. IP Routing Configuration Tasks Network 172.30.0.0 Network 160.89.0.0 IGRP, RIP Network 172.16.0.0 RIP Global configuration Select routing protocol(s) Specify network(s) Interface configuration Verify address/subnet mask

6. Defines an IP routing protocol router protocol [ keyword ] Router (config) # Dynamic Routing Configuration network network-number Router (config-router) # The network subcommand is a mandatory configuration command for each IP routing process

7. CONFIGURING OSPF

8. Router (config) # router ospf process-id OSPF Basic Configuration Commands Enables an OSPF routing process Router (config-router) # network address wildcard-mask area area-id Selects participating interfaces

9. OSPF Basic Configuration Example router ospf 63 network 172.16.5.3 0.0.0.0. area 1 network 172.16.0.0 0.0.255.255 area 0 network 192.168.10.5 0.0.0.0 area 1 Area 0 Area 1 172.16.1.1 172.16.3.2 192.168.10.5 E1 T0 E0 172.16.5.3 E2

10. Minimizes routing table entries Localizes impact of a topology change OSPF Route Summarization Area 0 Backbone ABRs Area 1 Summarization xx

11. O 131.108.4.0255.255.252.0 O 131.108.8.0255.255.252.0 O 131.108.12.0 255.255.252.0 O 131.108.16.0255.255.252.0 O 131.108.20.0255.255.252.0 O 131.108.24.0255.255.252.0 O 131.108.28.0255.255.252.0 Routing Table for B Routing Table for C IA 131.108.16.0 255.255.240.0 Inter-area (IA) summary link carries mask One entry can represent several subnets Route Summarization (cont.) Area 1 Area 0 ABR Summarization B AC

12. Summary Route 131.108.12.0 255.255.240.0 Mask = 240 Address = 12 Existing Subnet 131.108.12.0255.255.252.0 Mask = 252 Address = 12 11111100 000011 00 1111 0000 0000 1100 Valid 3rd Subnet Invalid Subnet Zero Some addresses may need reallocating Route Summarization Issue

13. Router (config-router) # area area-id range address mask Route Summarization Commands Consolidates IA routes on an ABR Router (config-router) # summary-address address mask Consolidates external routes on an ASBR

14. Route Summarization Example R2 R2# router ospf 100 network 172.16.64.00.0.31.255 area 2 network 172.16.96.0 0.0.31.255 area 0 area 0 range 172.16.96.0 255.255.224.0 area 2 range 172.16.64.0 255.255.224.0 R1# router ospf 100 network 172.16.32.0 0.0.31.255 area 1 network 172.16.96.0 0.0.31.255 area 0 area 0 range 172.16.96.0 255.255.224.0 area 1 range 172.16.32.0 255.255.224.0 172.16.64.0 - 172.16.95.0 255.255.255.0 Area 2 172.16.64.1 172.16.96.0 - 172.16.127.0 255.255.255.0 172.16.127.1 172.16.96.1 172.16.32.0 - 172.16.63.0 255.255.255.0 Area 1 172.16.32.1 Interface Addresses (255.255.255.0 mask) R1 R2 Area 0

15. Allows routing-information exchange between OSPF and other routing protocols OSPF Route Redistribution OSPF RIP IGRP Enhanced IGRP IS-IS BGP EGP

16. Router (config-router) # redistribute protocol [ process-id ] [ metric value ] [ metric-type value ] [ subnets ] OSPF Redistribution Command Redistributes routes from OSPF into other routing protocols (and vice versa)

17. OSPF Redistribution Example 1 Redistribution between RIP and OSPF RIP 172.16.9.1 172.16.8.1 172.16.62.1 172.16.63.1 OSPF Area 0 S0 S1 R1

18. OSPF Redistribution Example 1 router ospf 109 network 172.16.62.0 0.0.0.255 area 0 network 172.16.63.0 0.0.0.255 area 0 redistribute rip subnets metric-type 1 metric 20 router rip network 172.16.0.0 passive-interface serial 0 passive-interface serial 1 default-metric 10 redistribute ospf 109 match internal external 1 external 2

19. Redistribution Example 2 "Back door" creates potential loop RIP 172.16.9.1 172.16.8.1 OSPF Area 0 RIP Avoiding Loops R2 R3 R2 R1

20. Redistribution Example 2 cont router ospf 109 network 172.16.62.0 0.0.0.255 area 0 network 172.16.63.0 0.0.0.255 area 0 redistribute rip subnets metric-type 1 metric 20 distribute-list 11 out rip access-list 11 permit 172.16.8.0 0.0.7.255

21. VERIFYING OSPF OPERATION

22. Verifies interfaces are in correct areas Router# show ip ospf interface e 0 Ethernet0 is up, line protocol is up Internet Address 203.250.14.1 255.255.255.0, Area 0.0.0.0 Process ID 10, Router ID 203.250.13.41, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 203.250.15.1, Interface address 203.250.14.2 Backup Designated router (ID) 203.250.13.41, Interface address 203.250.14.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 0:00:02 Neighbor Count is 3, Adjacent neighbor count is 3 Adjacent with neighbor 203.250.15.1 (Designated Router) Loopback0 is up, line protocol is up Internet Address 203.250.13.41 255.255.255.255, Area 1 Process ID 10, Router ID 203.250.13.41, Network Type LOOPBACK, Cost: 1 Loopback interface is treated as a stub Host show ip ospf interface Command

23. Displays general information about the OSPF routing process Router # show ip ospf Routing Process "ospf 1" with ID 2.2.2.2 Supports only single TOS (TOS0) routes SPF schedule delay 5 secs, Hold time between two SPFs 10 secs Number of areas in this router is 1 Area 23 Number of interfaces in this area is 3 Area has no authentication SPF algorithm executed 19 times Area ranges are Link State Update Interval is 0:30:00 and due in 0:04:55 Link State Age Interval is 0:20:00 and due in 0:04:55 show ip ospf Command

24. Router# show ip ospf database OSPF Router with ID (3.3.3.3) (Process ID 1) Router Link States (Area 23) Link IDADV Router Age Seq# 3.3.3.3 78 0x80000032 4.4.4.4 1691 0x8000002B 1 2.2.2.2 1693 0x80000030 Checksum 0x80B6 0xE11C 0xE35E Link count 5 5 1.1.1.1 1696 0x80000026 0x80A1 1 Net Link States (Area 23) Link ID ADV Router Age Seq# Checksum 150.100.4.24.4.4.4 1691 0x80000030 0x2FCE 150.100.1.2 2.2.2.21693 0x80000024 0xFB29 show ip ospf database Command

25. Router>show ip protocol Routing Protocol is “ospf 300” Sending updates every 0 seconds Invalid after 0 seconds, hold down 0, flushed after 0 Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Redistributing: ospf 300 Routing for Networks: 183.8.0.0/0.0.255.255 144.253.100.0/0.0.0.255 Routing Information Sources: GatewayDistanceLast Update 144.253.100.01106d21 183.8.128.121100:17:32 192.3.63.1921100:17:33 192.3.63.1941100:17:33 183.8.128.01106d21 153.50.192.01100:17:33 153.50.193.11100:17:33 183.8.64.1301106d19 183.8.64.1281100:17:33 133.3.4.01100:17:33 131.108.100.31100:17:33 Distance: (default is 110) - - More - - show ip protocol Command

26. Router # show ip ospf virtual-links Other OSPF show Commands Displays parameters about OSPF virtual links Router # show ip ospf neighbor detail Displays neighbor information per interface Router # show ip ospf border-routers Displays routes to the ABR and ASBR