Detailed explanation of network foundation routing

Catalog

IP Routing basis

Classification of routing protocols

Routing rules

Static routing

Default route

OSPF Open shortest path first protocol

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IP Routing basis

Router

characteristic

An interface of a router is a network segment , A network segment is a broadcast domain

An interface of the router is used for a MAC Address

Routers can isolate broadcast domains

Broadcast messages cannot cross the router

What is a broadcast domain ？ The range that can receive the same broadcast message becomes the broadcast domain

Demon is a broadcast message ？ In the message IP Address /MAC The insulation with address as broadcast address indicates broadcast message

working principle

decapsulation ： View the purpose in the data frame MAC Whether the address is interfaced with your own MAC identical

check ： According to the purpose IP Address lookup routing table , If there is a purpose in the routing table IP Routing information of the network segment where the address is located

It will be forwarded according to the relevant routing information ; If there is no destination in the routing table IP The network segment where the address is located

Routing information , The router will directly discard this data

Repack ： Encapsulate the sending interface of the router and the device directly connected to the sending interface mac Address

Classification of routing protocols

AS： A collection of routers managed by the same organization using a unified group policy

Chinese government The civil code The Chinese people

Classify according to characteristics ：

Distance vector routing protocol ：rip、BGP（ Border gateway routing protocol ）

characteristic ：

Only care about distance and direction

Routing information is transmitted , Lack of understanding of global topology

It's easy to create loops

Link state routing protocol ：ospf( Open shortest path first protocol )、ISIS（ Intermediate system - Intermediate system ）

characteristic ：

It transmits link status information , Not passing routing information

Understand the global topology of the network

according to AS classification ：

AS External routing protocol ：ospf、isis、rip

AS Internal routing protocol ：BGP、

Routing rules

priority ： The smaller the numerical , The higher the priority , The better the path

The priority of direct connection routing is 0

Static routing priority is 60

Rip The priority for 100

Ospf The priority for 10

measurements ： The smaller the numerical , The less it costs , The better the path

The first measure ： Hops （ The number of routers , Every time you go through a router , Hop plus 1）

The loan ：cost= Actual bandwidth / Reference bandwidth

The longest match principle （ Precise matching ）

Select a path with a long subnet mask of the destination network segment to forward data

Characteristics of routing table ：

Only the best routes are stored in the routing table , Do not store available routes

When the optimal routing path fails , The router will write the available routes to the routing table for data forwarding

Static routing

Concept

Routing protocols manually configured and managed by network administrators

The difference between static routing and dynamic routing

The static routing protocol requires the network administrator to manually specify the destination network segment 、 Exit interface 、 Shock me , The dynamic routing protocol will learn the outbound interface required by the destination network segment by itself 、 Startle and other related routing information

Next jump definition ： The next router to reach the destination network segment has a direct interface with this router IP Address

Configure basic commands

<Huawei>system-view // <> Angle brackets indicate user views , Low authority , Unable to implement device configuration .

Use system-view Enter the system view

[Huawei] // [] Square brackets indicate that the system attempts , Have the highest authority , You can perform any configuration operation

[Huawei]sysname R1 // Modify the device name

[R1]int e0/0/1 // Enter under system view e0/0/1

[R1-Ethernet0/0/0]ip add 192.168.1.254 24 // Configure in the interface view IP Address

Display this // View the current configuration , It can be used under any attempt

Display ip interface brief // see IP Correspondence between address and interface

Display ip routing-table // see IP Routing table

Ip route-static Destination segment Destination segment mask Exit interface Next jump // Static route configuration command

Network failure

Request timeout! request timeout

There is no routing information of the target host

The target host does not exist in the network IP Address

Destination host unreachable

Check PC Whether the gateway configuration is correct  

Troubleshooting ideas

Display ip interface brief View device IP Whether the address configuration is correct

Display ip routing-table   Check the outbound interface of the destination network segment in the routing table 、 Whether the next jump is correct

Default route

Concept ： The destination network segment and subnet mask are 0

characteristic ： The default route can replace any one in the network IP Address or segment

Why can default routing replace all IP Address / Network segment ？

The network bit is 0— Host bit 32 position —2^32

experiment ·

OSPF Open shortest path first protocol

Distance vector routing protocol rip Characteristics

Only care about distance and direction

It's easy to create loops —30s Send update messages periodically — It contains routing information — Use hearsay mechanism to update the routing table

Rip It is measured by hops , Every time you go through a router , Hop plus 1,rip The maximum number of hops in 15,

If the number of hops corresponding to the destination network segment exceeds 15, Then the route is unreachable

Rip How to pass the routing table ： Hop by hop forwarding — Slow convergence

ospf How to improve rip The shortcomings of

rip The routing table is passed ,ospf It transmits link status information

rip The way to learn routing is to learn first and then transfer ,ospf The way to transmit link status information is to copy a copy and leave it in

Local , Deliver at the same time

rip The number of hops used as a measure , and ospf The link bandwidth is used as the measurement

Professional terms

LSA（link state adv Link status notification message ）、LSDB（link state database Link state database ）

Lsdb There are a lot of lsa

ospf How it works

function ospf, send out hello message , Build a neighborhood

function LSA flooding , Synchronize link state database

function spf Algorithm , Calculate the shortest path

ospf The role of each message

hello Message function

Discover the neighborhood

Build a neighborhood

ospf To configure

The direction of routing is opposite to that of data

ospf Why divide the area ？

Reduce LSDB Medium LSA, prevent LSA Too much leads to equipment downtime

ospf Rely on what to divide the region

ospf In, areas are divided by interfaces

Rules for dividing areas

Ospf Zhongjiang region is divided into backbone region and non backbone region , Area 0 Represents the backbone area ,

except 0 Areas other than represent non backbone areas . Communication between non backbone areas must be connected by backbone areas

Why must communication between non backbone areas be connected by backbone areas ？

Solve the loop problem between areas

ospf Configuration command

[R2]ospf Single zone configuration

[R2]ospf 100 // Get into ospf process 100 View

[R2-ospf-100]area 0.0.0.0 // Get into ospf Area view

[R2-ospf-100-area-0.0.0.0]network 12.1.1.0( Direct connection network segment ) 0.0.0.255( Unmask ) // Announce direct link network segment

Anti mask calculation method ：

255.255.255.255 Subtract the actual subnet mask of the network segment