[HCIA continuous update] overview of dynamic routing protocol

Overview of dynamic routing protocol

Classification of dynamic routing protocols

Sort by work area

IGP（ Internal gateway protocol ）

RIP

OSPF

IS-IS

EGP External gateway protocol

BGP

Classified by working mechanism and algorithm

Distance vector routing protocol

RIP

Link state routing protocol

OSPF

IS-IS

Distance vector routing protocol

1、 Routers running distance vector routing protocols periodically flood their own routing tables . Interaction through routing , Each router learns routing from its neighbors , And load it into your own routing table

2、 For all routers in the network , The router doesn't know the topology of the network , Just simply know where you want to go and where the direction is , How far is the distance . This is the essence of distance vector algorithm

Link state routing protocol

Different from distance vector routing protocol , The link state routing protocol advertises the link state rather than the routing table . A neighbor relationship of the protocol will be established between the routes running the link state routing protocol , Then they interact with each other LSA（ Link status report ）

Link state routing protocol —— LSDB To form a

Every router generates LSAS, The router will receive LSAS Put in your own LSDS（ Routing status database ）. The router goes through LSDB, Master the topology of the whole network

Link state routing protocol —— SPF Calculation

Each router is based on LSDB, Use SPF（ Shortest path first ） Algorithm to calculate . Each router calculates a tree with its own root 、 Acyclic 、 With the shortest path “ Trees ”. With this tree “ Trees ”, The router already knows the preferred path to every corner of the network

Summary of link state routing protocols

OSPF brief introduction

1、OSPF It is a typical link state routing protocol , It is widely used in the industry IGP One of the agreements

2、 Currently for IPV4 The protocol uses OSPF Version 2 （RFC2328）; in the light of IPV6 Agreement to use OSPF Version 3 （RFC2740） Unless otherwise specified, the subsequent references in this chapter refer to OSPF Are all OSPF Version 2

3、 function OSPF The interaction between routers is LS Information , Instead of direct interactive routing .LS Information is OSPF Key information for normal topology and routing calculation

4、OSPF The router will be in the network LS Gather information , Stored in the LSDB in . Routers know the network topology in the area , This is related to the calculation of acyclic paths by routers

5、 Each station OSPF All routers take SPF The algorithm calculates the shortest path to the destination . The router forms routes based on these paths and loads them into the routing table

6、OSPF Support VLSM（ Variable length subnet mask ）, Support manual routing and congregation

7、 The multi area design makes OSPF can Support larger networks

OSPF Application in campus network

OSPF Basic terms ：

Area

1、OSPF Area Used to identify a OSPF Region

2、 Area is the logical division of devices into different groups , Each group is identified by an area number

Router——ID

1、Router——ID, Used in a OSPF Uniquely identify a router in the domain

2、Router——ID The setting of can be configured manually , Or use the method of automatic configuration of the system

measurements

OSPF Protocol message type

OSPF Three major table items —— Neighborhood watch

OSPF There are three important items ,OSPF Neighborhood watch 、LSDB Table and OSPF Routing table . about OSPF My neighbor table , Need to know ;

• OSPF Before transmitting link status information , You need to establish OSPF Neighborhood
• OSPF Through interaction Hello Message establishment
• SOPF The neighbors table shows OSPF Neighbor status between routers , Use display ospf peer see

about OSPF Of LSDB surface , Need to know ：

1、LSDB Will save what they produce and receive from their neighbors LSA Information , In this case R1 Of LSDB Contains three LSA

2、Type identification LSA The type of ,AdvRouter ID send LSA The router

3、 Using the command line display ospf lsdb see LSDB surface