Collected By: Mehdi Daneshvar Supervisor: E.M.Kosari

Router

Routing

Routing Protocols Static Dynamic

Dynamic Routing Path Determination Metrics Convergence Load Balancing

Dynamic Routing Protocols IGP – Interior Gateway Protocol EGP – Exterior Gateway Protocol

Dynamic Routing Protocols Distance Vector Protocols RIP, IGRP Link State Protocols OSPF, IS-IS Path Vector Protocols BGP

OSPF

OSPF Network Broadcast Network Point-to-Point Network Non-Broadcast Multi-Access (NBMA) Point-to-Multipoint Virtual Links

Multi Access Designated Router-DR Backup Designated Router-BDR DROTHER

OSPF Designated Router Optimizing LSA flooding Process on multi-access links DR represent the multi-access network (by LSA2) and adjacency with others. Selection of DR is per interface. DR election : Higher priority (1-255) + higher RID Priority of 0 means no intention to become the DR or BDR DRothers send update packets to the AllDRouters ( ) All routers continue to multicast Hellos to the ALLSPFRouthers ( ) DR floods the updates to ALLSPFRouters ( )

OSPF PACKET TYPES Hello : Neighbor Discovery/Maintenance DBD : Database Description LSR : Database Download Request LSU : Database Update LSAck : Flooding Acknowledgement

Hello Packet

OSPF Finite State Machine Down Attempt (only on NBMA) Init – Hello is seen 2-Way – own RID is seen in Hello from neighbor ExStart – Master/Slave relation (highest RID) Slave sets MS-bit=0 Exchange – Database Description LSRs Loading – Transfer LSAs (LSR, LSU, LSAck) Full – Adjacent

Neighbor State

Neighbor Timers Fast Timer : Hello 10, Dead 40 Slow Timer : Hello 30, Dead 120

OSPF Router ID Each router OSPF router must have unique identifier = Router ID Router ID and LSA Sequence number are used to detect duplicate LSAs Router ID is highest IP address from any operational interface

OSPF Neighbors Area ID and Area Type Authentication Network Mask (Not P2P link) Hello Interval Router Dead Interval Option MTU

OSPF LSA Types Router Link State – Type 1 Network Link State – Type 2 Summery Link State – Type 3 Summery ASBR Link State – Type 4 AS External Network Link State – Type 5 NSSA External Network Link State – Type 7

OSPF AREAS Area 0 = Backbone Area Area x = non-transit flooding domain Stub Area = External routers are not flooded but internal summaries are. Totally Stubby Area = All Routers receive a default route only from ABR. Not-So-Stubby Area (NSSA) = External connection to another AS is permitted.

The routers in Area Internal Router Backbone Router ABR ASBR

OSPF Performancing Routers in the area : Max = 50 Router Neighbors : Max = 60 ABRs in the area : Max=3 Select one fast speed Interface for DR or BDR.

OSPF Virtual Link Allowing traffic to traverse from the backbone area to pas through another area. Must be configured between two ABRs. Transit are must have full routing table an cannot be a stub area.

OSPF Summary Developed by OSPF working group at IETF Classified as an IGP Uses IP Protocol 89 Dijkstra Algorithm to calculate SPF Metric Cost (per interface) ALLSPFRouters : ALLDRouters Default OSPF R Priority : 1 Full LSDB topology sync first, then partial LSA flooding. VLSM and Route tags are supported. Summarization at Area boundray.

OSPF vs. RIP OSPF Select Best Path Traffic Type of Service Hierarchical Routing Sender's Routing Table Authentication

Example Scenario

Net A to Net B: Send 1, 2, 4, 6, 7, 5, 3 Recive 3,2,1

Resources 1. RFC Wikipedia : 3. OSPF : 4. EIGRP & OSPF: 5. Forums of Cisco in persian: 6. Mohsen zoleh, BA Thesis :

Any question?