IP class notes (5)

Matching conditions

Specify router －－－ DR －－－ and MA Establish adjacency relationship with all other devices in the network

Back up the specified router －－－ BDR －－－ and MA Establish adjacency relationship with all other devices in the network

stay DR and BDR All exist under the clear condition , One MA You need at least four devices in the network to see the neighbor relationship .

DR and BDR Although it is called designated router （ Back up the specified router ）, But its scope of work is in a MA In the network , therefore , Its essence is the concept of interface .

Matching conditions －－－ stay MA In the network , If all equipment is adjacent , There will be a large number of repeated updates , therefore , Need to carry out DR/BDR The election of , All non DR/BDR（DROther） Only maintain the neighbor relationship between them .

DR/BDR The election of －－－ 1, Compare interface priorities , The highest priority is DR, The next largest is BDR.

The initial default value of priority is 1.

[r1-GigabitEthernet0/0/0]ospf cir-priority ? INTEGER<0-255>  Router priority value    If

Change the priority of an interface to 0, It means that the interface abandons DR/BDR The election of .

2, When priorities are the same , Then compare RID.RID The corresponding interface of a large router is DR, The next largest is BDR.

DR/BDR The election of －－－ Non preemptive election －－－ The election time is equal to a thousand deaths

<r1>reset ospf 1 process －－－ restart OSPF process

OSPF Data packets of

OSPF The agreement number of －－－ 89

ospf Message header

  edition －－－－ OSPF Version of protocol －－－－ OSPFv2 The version field is 2. type －－－－ OSPF The type of packet

Hello －－－ 1

DBD －－－ 2

LSR －－－ 3

LSU －－－ 4

LSACK －－－ 5

packet length －－－ Whole OSPF Length of data message , Unit byte .RID --- Indicates the router that sent this packet RID Area ID --- Of the area where the interface that sent the packet is located ID

Certification type and certification data －－－ OSPF At the time of certification , You need to compare the authentication type first , Only when the authentication type is the same can the authentication data be compared .

Authentication type －－－ null －－－ Null authentication －－－ 0

－－－ simple －－－ Plaintext Authentication －－－ 1

－－－ MD5 －－－ Compare summary value authentication －－－ 2

hello package －－－ Cycle discovery , Establish and maintain neighborhood relations .－－－ DR/BDR Elections also use hello package

  Subnet mask －－－ issue hello Package interface ip Mask information corresponding to the address －－－－ Huawei equipment sets that the subnet mask must be the same for both sides of neighbor establishment , Otherwise, you will not be able to establish a neighbor relationship （ Yes P2P The network does not work ）

hello Time and time of death －－－ Both neighbors hello The time and time of death must be the same , Otherwise, the establishment of neighbor relationship will fail .

optional －－－ 8 position ,8 Tag bits , Every tag bit swear 1, It means that it conforms to OSPF A certain characteristic of .

There is ospf Mark bit of special area , If the marker bits of special areas are different between neighbors , You will not be able to establish a normal neighbor relationship .

The priority of the router －－－ The interface that sent the packet has DR/BDR Priority at election .

Specify the router and backup the specified route －－－ I'm carrying DR/BDR Interface IP The earth

site .－－－－ stay DR/BDR Before it is selected , Use 0.0.0.0 To fill in . neighbor －－－ Local known neighbors RID.

hello Parameters in the package that restrict the establishment of neighbor relationships ---1, Subnet mask   2,hell Time 3,cieaci Time   4,ospf Marking of special areas 5, authentication

 DBD package －－－ Database description message －－－ 1, Using non data DBD Package for master-slave relationship election ;2, Use... That carries data DBD Package for directory information sharing .

MTU --- Huawei devices are not enabled by default MTU Value detection function , It can be used in the interface --- [r1-Serial4/0/0]ospf mtu-enable To open －－－－ If both sides are open MTU Value detection function , Then both parties MTU Values must be the same , The difference will remain exstart state , Cannot go down .

I --- init －－－ This bit swears 1, It stands for this DBD A packet is a data packet that elects a master-slave relationship , therefore , Such a packet does not contain LSA Head content . －－－ Before the master-slave relationship is selected , All devices consider themselves Masters

M --- more －－－ This bit swears 1, It means there are others behind DBD Package to send .

MS --- Master －－－ This bit swears 1, It means that the device sending this packet is the main .

Serial number －－－ stay DBD In the process of message sending and receiving , Will add... One by one 1, Use thousands to ensure DBD Order and reliability of message transmission .

LSR package －－－ Link status request message －－－ Ji Qian DBD Package request local unknown LSA Information

 

Link state type , Link state ID, Notify router －－－－ “LSA A triple ” －－－ Three parameters can uniquely identify one LSA.

LSU package －－－ Link state update message －－－－ Really carry LSA Packets of information

LSACK package －－－ Link status acknowledgement message

OSPF The interface network type of P2P

MA         BMA NBMA

OSPF The interface network type of －－－ refer to ospf Interfaces work in different default modes under different network types .

Network type	ospf The network type of the interface （ Operation mode ）
BMA（ Ethernet ）	Broacicast, Multiple neighbors can be established . Need to carry out DR and BDR The election ,hello 10S,dead time 40S
P2P（PPP, HDLC）	P2P, Only one neighborhood can be established , There is no need for DR and BDR The election ,hello 10S,dead time 40S
Loopback interface （ Virtual interface ）	P2P, Huawei equipment is defined as P2P type , But in fact, there is no data sending and receiving . Loopback interface default learning 32 Bit host routing
	P2MP, Multiple neighbors can be established , There is no need for DR and BDR The election of ,hello 30S,dead time 120S. Learn the host routing of neighbor interface .
NBMA（ In the frame	NBMA, Multiple neighbors can be established , Need to carry out DR and BDR choose

[r2]ciisplay ospf interface GigabitEthernet 0/0/0 －－－ see OSPF The interface network type of

T1 －－－ 1.544Mbps

E1 －－－ 2.048Mbps －－－－ By default, the serial port of Huawei devices follows E1 standard .

Huawei equipment defines the cost value of the loopback interface as 0, Will not be affected by the outside world , Not affected by the change of reference bandwidth .

[r2-LoopBack0]ospf network-type broacicast －－－ Modify the interface network type

If you want to restore the true mask length of the loopback interface , You can change the network type of the loopback interface to broacicast.

Huawei equipment will tunnel The transmission rate of the interface is defined as 64Kbps －－－－ The main purpose of this design of Huawei equipment is to increase the overhead value of tunnel interface , Avoid sending data from the tunnel interface as much as possible , Because the data of tunnel interface , The reality is still sent from the physical interface , But it will increase the complex process of packaging and unpacking , Increase the waste of resources .

stay MGRE In the environment of , There is also a fully connected mesh topology －－－ mesh, That is, all boundary devices are the center , Also Branch , Built like this MGRE The environment is similar BMA Network environment .

[r1-ospf-1]peer 12.0.0.2 －－－ Unicast neighbors , stay NBMA In this environment, you can manually specify the neighbor relationship .

Attempt －－－ Try status －－－ Transition state －－－ After the local side manually specifies the neighbor, it will start from down Reach the trial state , after , After the opposite end is manually specified, it will enter the next state .