Shulou(Shulou.com)06/01 Report--

Overview

Autonomous system (AS)

Interior Gateway Protocol (IGP) (including RIP,OSPF,ISIS)

External Gateway Protocol (EGP) (including BGP) Alibaba, commonly known as Flying platform

OSPF is a link-state routing protocol

OSPF (shortest path first selection Protocol) working process

The shortest path: the lower the path cost, the higher the bandwidth. Learning link state information all the time

OSPF region

OSPF region (Area 0 is the backbone area, there is one and only one, and the other areas are non-backbone areas)

In order to adapt to large networks, OSPF divides multiple areas within the AS

Each OSPF router maintains only complete link-state information in its area

Regional ID

The region ID can be expressed as a decimal number

It can also be expressed as a decimal number

Backbone area Area 0

Responsible for inter-area routing information dissemination

Router ID

The IP address that uniquely identifies the router in the OSPF area

Router ID selection rules

1. Select the IP address with the highest value on the router lookback interface

two。 If there is no lookback interface, select the one with the highest IP address in the physical port

3. You can also use the router-id command to specify Router ID (manually selected)

TIP: the second is not recommended (addresses on loopback are always useful except for a row of routing addresses that are down)

DR (primary) and BDR (backup)

The network topology is more reliable, and there can be no problems with the central routing of the star structure, otherwise all routes will not work properly.

Other routers (DRothers) only form adjacencies with DR and BDR

The election method of DR and BDR

1. Automatically elect DR and BDR

(1) the router with the largest Router ID on the network segment will be elected DR, and the second largest router will be elected BDR.

two。 Manually select DR and BDR

(1) the priority range is 0-255. The higher the value, the higher the priority. The default is 1.

(2) if the priority is the same, Router ID needs to be compared.

(3) if the priority of the router is set to 0, it will not participate in the election of DR and DBR.

The election process of DR and BDR

The priority of a router can affect an election process, but it cannot force the replacement of an existing DR or BDR router

Multicast address of OSPF

224.0.0.5: bearer address, DR and BDR send the wrong address to other routes (for voice calls)

224.0.0.6: listen for feedback from other routes.

(RIPv2:224.0.0.9)

The measure of OSPF is COST

COST=108/BW

The shortest path is calculated based on the cost specified by the interface (cost)

The lower the TIP:Cost value, the better. The metric is bandwidth.

OSPF packet

Carried in an IP packet, using protocol number 89

Package type of OSPF

The first stage of OSPF startup is the process of establishing two-way communication using Hello messages.

Seven states

1. Down status: before confirming the neighbor status without saying hello

2. Init status: activated after receiving the hello packet

3. 2-Way status: establish interaction (elect DR and BDR, select only the two largest, but not sure DR and BDR)

4. ExStart: quasi-startup status (determine DR and BDR identity)

5. Exchange status: exchange data (DBD message, LSAck)

6. Loading status: load (data type: LSR/LSU/LSA/LSAck)

7. Full status: convergence

OSPF divides networks into four types

1. Point-to-point network

two。 Broadcast multiaccess network

3. Non-broadcast multiaccess network

4. Point-to-multipoint network

Consider the use of OSPF from the following aspects

1. Network scale

two。 Network topology

3. Other special requirements

4. Router's own requirements

Characteristics of OSPF

1. Adaptable to large-scale network

two。 Fast convergence speed of route change

3. No routing ring

4. Support variable length subnet mask VLSM

5. Support for zoning

6. Support for sending protocol packets with a multicast address

Comparison between OSPF and RIP

The trust degree of Ospf is 110 and rip is 120.

Ospf multi-area configuration

Reasons for generating OSPF Multiregions

1. Improve the scalability of the network

2. Fast convergence

Area division is based on the interface of the router; ISIS is divided by route.

Configuration commands for OSPF

Start the OSPF routing process

Router ospf process-id (process number)

Specify the interface and area on which the OSPF protocol runs

Network address inverse-mask (anti-mask) area area-id (area number)

Modify the priority of an interface

Ip ospf priodity priodity

Modify the cost value of the interface

Ip ospf cost ccost

View routing tabl

Show ip route

View the list of neighbors and their status

Show ip ospf neighbor

View the configuration of ospf

Show ip ospf

View the data structure of the ospf interface

Show ip ospf interface type number

Inter-domain (ABR, ASR)

Summarize OSPF routing protocols

Four routing types: DR, BDR, ABR, ASBR

Five regions: backbone area, standard area, stub area, stub area, non-stub area

Five big data bag types: hello, DBD, LSR, LSU (LSA), LSACK

Six link-state advertisements (LSA): type1, type2, type3, type4, type5, type7

Seven states: down, init, 2-way, exstart, exchange, loading, full.

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