Routing table Real routing table Codes C connected

Routing table

Real routing table Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N 1 - OSPF NSSA external type 1, N 2 - OSPF NSSA external type 2 E 1 - OSPF external type 1, E 2 - OSPF external type 2, E - EGP i - IS-IS, L 1 - IS-IS level-1, L 2 - IS-IS level-2, ia - IS-IS inter area * - candidate default, U - per-user static route, o - ODR P - periodic downloaded static route O E 1 202. 39. 232. 0 [110/1611] via 211. 1, 00: 09: 46, Gigabit. Ethernet 2/2 O IA 211. 224. 8 [110/511] via 211. 1. 1. 3, 00: 06: 16, Gigabit. Ethernet 2/1 S 192. 168. 4. 68 [1/0] via 10. 76. 37. 1 10. 0/8 is variably subnetted, 23 subnets, 6 masks C 10. 76. 0. 64/27 is directly connected, Fast. Ethernet 0/1

Open Shortest Path First routing protocol: link-state: ISIS、OSPF Distance vector: RIP、IGRP 屬於link-state ，負責傳遞routing table ，讓 封包透過最短路徑傳送

link-state database It has a map of every router, its links, and the state of the links. It also has a map of every network and every path to each network. There are same link-state database in every router

Ospf packet format Hello DD(database descriptor ) LSR(link-state request) LSU(link-state update) LSAck(link-state Acknowledgment)

OSPF Topologies Broadcast Multiaccess Point-to-Point NBMA X. 25 Frame Relay

Broadcast Multiaccess DR BDR

Electing the DR and BDR P=3 P=2 DR BDR Hello P=1 P=0 • Hello packets exchanged via IP multicast

Neighborship D E Hello B A afadjfjorqpoeru 39547439070713 Hello C Router ID *Hello(10)/dead intervals(40) Neighbors Area-ID Router priority DR IP address BDR IP address Authentication password Stub area flag * * *

Discovering Routes DR E 0 172. 16. 5. 1 afadjfjorqpoeru 39547439070713 Hello 172. 16. 5. 3 Exstart State I will start exchange because I have router ID 172. 16. 5. 1. No, I will start exchange because I have a higher router ID. afadjfjorqpoeru 39547439070713 Hello

Discovering Routes DR E 0 172. 16. 5. 1 afadjfjorqpoeru 39547439070713 Hello 172. 16. 5. 3 Exstart State I will start exchange because I have router ID 172. 16. 5. 1. No, I will start exchange because I have a higher router ID. Exchange State Here is a summary of my link-state database. afadjfjorqpoeru 39547439070713 Hello afadjfjorqpoeru 39547439070713 DBD Here is a summary of my link-state database.

Discovering Routes (cont. ) DR E 0 172. 16. 5. 1 172. 16. 5. 3 afadjfjorqpoeru 39547439070713 LSAck afadjfjorqpoeru 39547439070713 Thanks for the information! LSAck

Discovering Routes (cont. ) DR E 0 172. 16. 5. 1 172. 16. 5. 3 afadjfjorqpoeru 39547439070713 LSAck Thanks for the information! LSAck Loading State afadjfjorqpoeru 39547439070713 LSR I need the complete entry for network 172. 16. 6. 0/24. afadjfjorqpoeru 39547439070713 Here is the entry for network 172. 16. 6. 0/24. afadjfjorqpoeru 39547439070713 LSAck Thanks for the information! LSU

Discovering Routes (cont. ) DR E 0 172. 16. 5. 1 172. 16. 5. 3 afadjfjorqpoeru 39547439070713 LSAck Thanks for the information! LSAck Loading State afadjfjorqpoeru 39547439070713 LSR I need the complete entry for network 172. 16. 6. 0/24. afadjfjorqpoeru 39547439070713 Here is the entry for network 172. 16. 6. 0/24. afadjfjorqpoeru 39547439070713 LSAck Thanks for the information! Full State LSU

Choosing Routes 10. 1. 1. 0/24 A 10. 2. 2. 0/24 B 10. 3. 3. 0/24 C Cost=6 Cost=10 10. 4. 4. 0/24 Topology Table Net Cost Out Interface 10. 2. 2. 0 6 To 0 10. 3. 3. 0 7 To 0 This is the best route to 10. 3. 3. 0 10 E 0

OSPF Terminology Autonomous System Neighbors Interfaces Area 1 Cost = 10 Cost = 1785 Area 0 Cost = 6 Neighborship Database Lists Neighbors Topology Database Lists All Routes Routing Table Lists Best Routes

Maintaining Routing Information Link-State Change DR x 1 LSU A B • Router A tells all OSPF DRs on 224. 0. 0. 6

Maintaining Routing Information 2 Link-State Change LSU x DR 1 LSU A B • Router A tells all OSPF DRs on 224. 0. 0. 6 • DR tells others on 224. 0. 0. 5

Maintaining Routing Information 2 Link-State Change LSU x DR 1 LSU A B 3 LSU • Router A tells all OSPF DRs on 224. 0. 0. 6 • DR tells others on 224. 0. 0. 5

Maintaining Routing Information 2 Link-State Change LSU DR 4 I need to update my routing table. x 1 LSU A B 3 LSU • Router A tells all OSPF DRs on 224. 0. 0. 6 • DR tells others on 224. 0. 0. 5

Point-to-Point Neighborship • Router dynamically detects its neighboring router using the Hello protocol • No election: Adjacency is automatic as soon as the two routers can communicate • OSPF packets are always sent as multicast 224. 0. 0. 5

Configuring OSPF on Internal Routers Broadcast Network A E 0 10. 64. 0. 2 10. 64. 0. 1 E 0 <Output Omitted> interface Ethernet 0 ip address 10. 64. 0. 1 255. 0 ! <Output Omitted> router ospf 1 network 10. 0 0. 255 area 0 Can Assign Network or Interface Address. Point-to-Point Network B S 0 10. 2. 1. 2 10. 2. 1. 1 S 1 C <Output Omitted> interface Ethernet 0 ip address 10. 64. 0. 2 255. 0 ! interface Serial 0 ip address 10. 2. 1. 2 255. 0 <Output Omitted> router ospf 50 network 10. 2. 1. 2 0. 0 area 0 network 10. 64. 0. 2 0. 0 area 0

configuration router rip network 140. 100. 0. 0 redistribute ospf 100 metric 3 router ospf 100 network 140. 100. 0. 0 redistribute rip 100 metric 3

Issues with Maintaining a Large OSPF Network OSPF The SPF is running too often for me to route. I am only receiving LSAs, no data. OSPF My routing table is too big, I am running low on memory. OSPF

The Solution: OSPF Hierarchical Routing Area 0 Area 1 Area 2 Autonomous System • Consists of areas and autonomous systems • Minimizes routing update traffic

OSPF Multi-Area Components Routers LSAs Areas afadjfjorqpoeru 39547439070713 Internal Type 1 Area 0 I am a backbone. afadjfjorqpoeru 39547439070713 Type 2 ABR afadjfjorqpoeru 39547439070713 Area 1 I am standard. Type 3/4 ASBR afadjfjorqpoeru 39547439070713 Type 5 Backbone Area 2 I am a stub.

Types of OSPF Routers Area 1 Backbone Area 0 Area 2 ABR and Backbone Router Backbone/ Internal Routers ASBR and Backbone Router External AS ABR and Backbone Router

LSA

type