Chapter11OSPF

OSPF 111 OSPF Link state Interior Gateway Protocol OSPF 1988 IETF OSPF workgroup OSPF RFC 2383 version 2 Chapter OSPF Version 2 OSPFIGP AS 1 1111 Convergence Traffic Distance Vector Link state OSPF (Flooding), OSPF RIP 1112 CIDR, VLSM OSPF RIP version 1 CIDR, VLSM IP 1113 Hops 15 RIP OSPF OSPF 1114 Routing Table Simple Password 2 RIP OSPF Simple OSPF Password Password Rogue Router 1115 OSPF 224005 224006, 30 RIP 1 OSPF AS Area, Area Area 2 Password

WAN 1116 Hops 3 RIP IP OSPF ( ) Cost 1 Hops 1 Cost 112 OSPF Link State OSPF 2 (Area) Link state Link state database Root Shortest Path Tree 3 RIP Next Hop Chapter 9 RIP

2 Shortest Path Tree ASOSPF Area AS(Autonomous System)Area area AS Area Area Area OSPF Link, Link state database Shortest Path Tree 1121 4 OSPF, OSPF OSPF A Autonomous System(AS) B Interface(link): (Low level) 4 RFC 2383 wwwciscocom

Unnumbered Connection 5 IP C Link State ( ) Hello LSA(Link State Advertisements) D Router ID OSPF 32bits AS E Hello F Network IP Network/ subnet/ supernet Network ID Point to Point G Area AS Area ID Area OSPF Link State H Cost Link (Metric) Cost Outbound I Neighborship Database J Link-state Database(Topology database) Link-state LSA Area Link-state database K Routing Table Link state database Shortest Path First(SPF, Dijkstra 6 ) Forwarding database OSPF 5 Point to Point Serial IP Ethernet IP 6 Link State

L Broadcast Networks, M Point to Point Networks T1 N Non Broadcast Multiple Access(NBMA) networks Broadcast Frame Relay, X 25 3 OSPF Link Topology O Neighboring Router OSPF Hello P Adjacency Q Flooding OSPF Link-state database OSPF RIP LSA

Flooding R Designated Router Broadcast NBMA Designate Router Hello Broadcast OSPF (adjacency) 6 15 Adjacency LSA, Multiple Access Designate Router Designated RouterLink state Database S Lower-Level Protocols IP OSPF Network Access, Frame Relay 4 OSPF Chapter Area OSPF OSPF Link state

Distance Vector ( ) OSPF Area OSPF 1 OSPF Link Hello 2 LSA Hello Link state OSPF Link State LSA 3 LSALink State Database Area LSA OSPF Link State Database Shortest Path Tree, (Neighbro) (Adjacency)? AS Area, Neighbor neighbor Adjacency 7 1122 OSPF 7 OSPF

5 OSPF OSPF 5 IP OSPF 5 ( 1 ) OSPF OSPF 6 OSPF Packet Header

Version No: OSPF Type: OSPF Type 1 2 3 4 5 Description Hello Database Description Link State Request Link State Update Link State Acknowledgment 1 OSPF Type Value Packet Length: OSPF byte OSPF Router ID: ID Area ID: 32bits Area Authentication type: OSPF Authentication Type Value 0 1 2 All Others Description (Null Authentication) Password(Simple Password) (Cryptographic MD 5 Authentication) 2 Authentication Type

7 IP Header and OSPF Header Format 7 OSPF Hello OSPF IP TTL 1 OSPF, Flooding OSPF 113 OSPF Operation 1131 OSPF OSPF Link State OSPF Hello OSPF Neighbor Relationship Hello IP 224005(AllSPFRouter Address) Hello 5 A Hello Protocol

8 Hello Packet Format Router ID: 32bits Router ID AS IP IP Router id 2 OSPF IP 19216811 192168121192168121 Router ID HelloInterval: OSPF Hello (Multi access Network 10 ) Router Priority: 8 bits OSPF Designated Router( DR) Backup Designated Router( BDR), DR BDR OSPF DR BDR Router Dead Interval: OSPF Hello, Dead Interval Dead Interval Hello interval 4 Neighbors:, Hello,

DR and BDR IP address: DR BDR IP Authentication Password: OSPF, Password B 9 OSPF Exchange Process OSPF Link 1 A Down State A Hello, A 2 OSPF ANeighbor Init state A 3 A Hello Unicast A Hello Hello, A,, B A, C 4 Hello A

Neighbor Database Two way state OSPF,,, (Broadcast Network), Point to Point, ( ^^) NBMA ( Point to Point? ^^), C Designated Router and Backup Designated Router 10 DR BDR OSPF (Adjacency), LSA OSPF Point to Point

Multiple Access( ) 8 OSPF Convergence OSPF Link state Designated, Designated Router Designated Router Backup Designated Router BDR Link State DR DRBDR 9 DR BDR OSPF 8 Link-state DR BDR Link state DR BDR Priority Router Priority DR BDR Priority ID DR OSPF 1 ID DR 0 DR BDR (DR BDR Drother ), DR DR BDR, DR BDR BDR DR, DR LSA BDR DR Multiple Access OSPF, DR BDR DR, BDR DR

11 Broadcast DR/BDR 12 NBMA DR D 8 DR BDR OSPF exstart state Exstart state DR 8 Point to Point DR/BDR Point to point

BDR ID (Master) (Slave) (ID ) Exstart state Sequence No Database Description (DBD) exchange state 11 DBD Link state LSA (LSA Header) Link-state, LSA Sequence Number LSA Sequence DD Sequence Database Description 13 Database Description Packet Format Interface MTU: MTU Database Description

Virtual Link 0 Options: I-bit: 1 Database Description M-bit: More bit 1 Database Description MS-bit: Master/Slave bit 1 DD Sequence Number: Database Description Database Description DBD DBD Sequence LSA Acknowledgement DBD LSA, Link State Request (Loading state) Link State Request OSPF Link State Update Link State Update Link state database Shotest Path Tree Full state Full state,, Hello, 30 LSA

14 E Dijkstra 9 Shotest Path First Tree LSA Link State DatabaseOSPF Dijkstra SPF Tree(Shortest Path First Tree) SPF Tree 15 Sample AS Diagram 14 AS AS Area 9 Dijkstra RFC 2328 161

AS Full state Dijkstra Cost SPF Tree Graph 3 FROM Rt1 Rt2 Rt3 Rt4 Rt5 Rt6 Rt7 Rt8 Rt9 Rt10 Rt11 Rt12 N3 N6 N8 N9 Rt1 0 Rt2 0 Rt3 6 0 Rt4 8 0 Rt5 8 6 6 Rt6 7 5 Rt7 6 0 Rt8 0 Rt9 0 Rt10 7 0 0 Rt11 0 0 TO Rt12 0 N1 3 N2 3 N3 1 1 1 1 N4 2 N6 1 1 N7 4 N8 3 2 N9 1 1 1 N10 2 N11 3 N12 8 N14 8 N 15 9 3 Directed Graph (Rt: Router, N: Network) 3 AS (F RO M)

st Co 12 LSA 10 From RT12 N9 N10 To RT12 N9 1 N10 2 4 12LS A 4 A LS O SPF 3 15 SPF Tr ee 6 SPF Tree 10 LSA LSA LSA LSA 115 LSA

16 6 SPF Tree SPF Tree,, Cost SPF Tree OSPF F SRF Tree Routing Table,, AS Area OSPF Routing Table(Forward Table) LSU Link State database OSPF ( 5 ) PSTN,, OSPF LSU,

OSPF ospf SPF Tree ( Forwarding Table) OSPF Cost Load balancing Cost 11, OSPF IP 12 156 Destination Next Hop Cost N1 RT3 10 N2 N3 N4 Interface A Interface B N6 N7 N8 N9 N10 N11 RT5 RT7 RT3 RT3 RT3 RT10 RT10 RT10 RT10 RT10 RT10 RT10 RT5 RT10 10 7 8 12 7 8 12 10 11 13 14 6 8 5 6 12 5, 7, 12 AS 6 11 RFC 2328 Cost Cisco 10 8 Cost, / 100M Cost=1 12 4 Load Balancing 6

5 13 OSPF Network Router 5 Nxx Network entry RTx Router Entry Network Entry, uter En Ro try Area Border Router(ABR ) AS Border Router(ASBR) OSPF Area AS, R AB ASBR Path Type OSPF Intra Area, Inter Area, Type 1 External, Type 2 External 4 116 Area Intra Area: OSPF Area Inter Area: OSPF AS Area Type1 External: AS Type 1 OSPF AS BR Cost ASBR ( 17 ) Type2 External: AS Type OSPF SBR A Cost Metric, ASBR AS BR Cost 17 ASBR D Type 1 BASBR Type2 C ASBR 13 Area AS 116 Area

17 Type External Path Routing Talbe OSPF IP, IP 19216810100 192168100 /24, 1921681064/26 OSPF 1921681064/26 Path 1 Intra Area Path, 2 Inter Area Path, 3, E1 External Path, 4 E2 External path 14 G Routing OSPF Area Link state link state update 14 LSA LSU 115 LSA

, Area Flooding Flooging Process LSA 006( 224 DR BDR) Link state Update DR LSA ACK LSU Flooding (224005) Flooding LSU ( ) LSA ACK DR, LSU Flooding ( Multiple Access DR Point to Point Flooding ) LSA LSU Link state database 18 LSU H Flooding

19 Adjacencies OSPF 19 OSPF Link State, LSU LSA LSU, OSPF LSAck ( 20)

20 OSPF Link state Update LSAck OSPF LSU Flooding OSPF Link state Area AS(Area ), Link state database OSPF Flooding OSPFFlooding Acknowledgments Link state Update, LSA OSPF,, LSA LSA OSPF LSU LSA Ack Ack Ack LSA, Ack

Sequencing, Checksum, and Aging LSA Sequence No Checksum, age Sequence No LSA, LSA, Checksum LSA Checksum LSA (Age Flooding ) Link state Database 5 Link state database Age LSA 3600, 1 0 Age LSA LSA Flooding LSA age, 1 OSPF LSA OSPF OSPF Topology OSPF 1132 OSPF Operation A Point to Point Point to Point OSPF Broadcast DR/BDR Point to Point OSPF 224005 Hello, DR Point to Point IP Unnumbered Interface Point to Point OSPF oint to Point B Non Broadcast Multiple Access Broadcast Multiple Access, Frame Relay, OSPF, VC

OSPF Unicast NBMA OSPF A Nonbroadcast Multiple Access(NBMA)- OSPF Broadcast DR/BDR B Point to Multipoint VC Point to Point DR/BDR C 114 Area 1141 Area 21 Area AS Link state, Convergence Link state LSA Database, LSA Flooding RIP, RIP OSPF RIP OSPF OSPF OSPF

Area AS AS Area, Area Area, Area, Area OSPF C D Link State Database LSA CPU E Link State Database Area LSA Flooding 1142 area ID AS Area 32 bits Area id IP 4 Octec Area ID Area 00120 IP ID, Area 00120 Area 276 Area 0000 AS Area ID OSPF Area Area, Area AS Area Area Area OSPF AS Area Area Area Area OSPF AS Intra Area Traffic, Inter Area Traffic, External Traffice 114 3 Router Type

22 OSPF Router types OSPF AS A Internal Router Area Link state database B Area Border Router(ABR) Area ABR Area Inter Area ABR, AreaLink state Database ABR Area C Backbone Router Area Area 0000 Backbone Router ABR Backbone D Autonomous system Boudary Router(ASBR) External ( BGP), ASBR OSPF AS Area

1144 Virtual Link 23 Virtual Link Virtual Link Area Area Non Backbone Area 23 Area 4 Area, Area 3 Virtual Link Non backbone Area Area Non Backbone Area(Transit Area) ABR Virtual Link AS, Hello Interval, Dead Interval 115 Link state Database LSAOSPF LSA Link State Database Link State DatabaseLSA 1151 LSA Type OSPF AS LSA Area ABR

Area LSA Area LSA OSPF LSA 11 Type Code 1 2 3 4 5 6 7 8 9 10 11 Description Router LSA Network LSA Network Summary LSA ASBR Summary LSA AS External LSA Group Membership LSA NSSA External LSA External Attribute LSA Opaque LSA(Link-local scope) Opaque LSA(Area-local scop) Opaque LSA(AS Scope) 6 LSA Type A Router LSA(type 1) Router 24 LSA Router LSA OSPF LSA OSPF LSA ID,, Cost

Router LSA LSA Area Flooding B Network LSA(type 2) 25 Network LSA Network LSA Multiple Access DR LSA 25 DR (DR ) DR DR LSA Router LSA DRArea Flooding C Network Summary LSA(type 3)

26 Network Summary LSA Network Summary LSA ABR ABR Area ABR Area Network summary LSA Area ABR Area AreaABR ABR Network Summary LSA Area ABR Network Summary LSA, 26 Cost LSA Cost LSA ABR Area Cost Area, Area Area ABR network Summary LSA SPF Tree ABR Cost LSA Cost D ASBR Summary LSA(type 4)

27 ASBR Summary LSA ASBR Summary LSA ABR LSA ASBR 27 ASBR Summary LSA ID ID ASBR, E Autonomous System External LSA(type 5)

28 AS External LSA External LSA Network Summary LSAAS Network Summary LSA AS Area External LSA AS, AS Default Route LSA ASBR F Group Membership LSA(type 6) Group Membership LSA 15 1152 Stub Area 16 15 Chapter 15 IGMP 16 Stub Area Area Link State Database AS External LSA

29 Stub Area ASBR AS AS External LSA AS AS AS External LSA AS, External Link state 29 Area 4 Area 4 Area ABR External LSA Area Stub Area Stub Area ABR Network Summary LSA Default RouteInternal Router External LSA Stub Area AS Stub Area Link state Database Stub Hello Packet Flag E-bit 0 stub router Virtual Link

Stub Area ASBR Stub Area ABR Defult Route ABR ASBR 30 Stub AreaLSU Flooding 116 Link State OSPF Distance Vector OSPF ASArea OSPF RIP AS Area, OSPF OSPF ( ), Link state IS-IS? Link State