review HCIA：

One 、TCP/IP Model ,OSI Model

OSI Open system interconnection reference model

Applications process data — The top three
application layer Abstract language —> code
The presentation layer code —> Binary system
The session layer Address discrimination within the application （ No standard format ）
The lower four layers are the data transmission layer
Transport layer TCP/UDP – piecewise （ suffer MTU Limit ）、 Port number
The network layer IPV4、IPV6 -- Internet Protocol Logic Addressing
Data link layer Control the physical layer （ Media access control ）
The physical layer

requirement ： bridge — Switch — Working in the media access control layer
0、 Provide port density
1、 Unlimited transmission distance
2、 There is no conflict — All nodes can send and receive their own data at the same time
3、 unicast — One to one transmission of data

Two 、 How switches work ：

1、 When the data frame enters the switch , The switch first looks at the source in the data MAC Address , Then connect the data entry interface with the mac Mapping records to local MAC In the table ; Then view the target in the data frame mac Address , Based on goals mac Address check local mac surface ; If there is a record in the table, the data will be forwarded only from the interface of the record ;– unicast
2、 If there is no target mac The interface record corresponding to the address , The data will be flooded — In addition to the flow access interface , All other interfaces copy out ;

3、 ... and 、IPV4 Address

32 Bit binary Dotted decimal mark

【1】 There is ABCDE classification ;

among ABC For unicast address — It can be used as a source , It can also be a goal ;
D For multicast — Only as a target ;E For the sake of reservation ;
Based on the first 8 Bit classification ：
A 1-126
B 128-191
C 192-223
D 224-239
E 240-255

Special address ：

1、127.0.0.1 Loopback address Test use
2、0.0.0.0 Default route - On behalf of all Invalid address — It means there is no
3、255.255.255.255 Restricted broadcast address
4、 The host bits in each segment of the address are all 0; whole 1;
192.168.1.0/24 All the hosts 0— network number
192.168.1.255/24 All the hosts 1— Direct address
5、169.254.0.0/16 Automatic private address 、 Local link address

【2】VLSM Variable length subnet mask

— By extending the length of the subnet mask ; A network number is logically divided into multiple ;– Subnet partition

【3】CIDR— Classless inter domain routing

— Take phase parity , Go to different places ; Connect multiple network numbers ; The synthesis of logic is a ;

Subnet summary ：

After summary , The subnet mask of the summary network segment , Longer than or equal to the main class mask length

HYPERNET ：

After summary , The subnet mask of the summary network segment , Shorter than the main class ;

Four 、 Static routing

1、 Basic configuration

[Huawei]ip route-static 1.1.1.0 24 12.1.1.2
[Huawei]ip route-static 2.2.2.0 24 GigabitEthernet 0/0/1
                     Target network number     Next hop or exit interface 

Next jump ：

After the traffic is sent locally, the next router interface to enter ip Address ;

Exit interface ：

The interface where traffic is sent from the local router ;

Suggest ：

stay MA It is suggested to write the next hop in the network ; In the point-to-point network, it is suggested to write the interface
MA Multiple access to the network — In a network segment , The number of nodes is unlimited
Point to point — In a network segment , The number of nodes can only be two

2、 Summary

When reaching a partially continuous subnet , If based on the same next hop access ; These target networks can be summarized and calculated ; Only configure the route to the summary network segment — Reduce the number of routing table entries

3、 Routing black holes

When the summary address contains address segments that do not currently exist in the network ; Traffic that should have been discarded long ago , It still needs to spread in the network for a period of time ; Can be discarded , Wasted link resources ;– Try to plan reasonably ip Address , Accurate summary calculation ;

4、 Default route

A route that does not limit the destination ; When looking up the table , After the router queries all local direct connections 、 static state 、 After dynamic routing , If there is still no reachable path, use this entry ;

5、 Air interface anti loop routing

When the router black hole meets the default route , There must be a loop ;

[R1]ip route-static  1.1.0.0 22 NULL 0

6、 Floating static routing

By modifying the default priority , Play the effect of static route backup

[r2]ip route-static  1.1.0.0 22 23.1.1.1 preference 61

The default static routing priority is 60; The smaller the better.

The default static routing priority is 60; The smaller the better.

7、 Load balancing

– When a router accesses the same destination , Have Multiple paths with similar overhead when ; The device can split the traffic and delay multiple paths for simultaneous transmission , Play the role of bandwidth superposition ;

5、 ... and 、 The basic configuration of the equipment

<Huawei>     <> It represents the pattern of the present , Different modes have different configuration permissions 
<Huawei>   User view 、 User mode  ---  You can view all the parameters of the device 

<Huawei>system-view 
[Huawei]   The configuration view   --  The device can be managed and configured 

[Huawei]interface GigabitEthernet 0/0/0   Enter an interface 
[Huawei-GigabitEthernet0/0/0]ip address 192.168.1.1 255.255.255.0   Configuration interface ip Address 
<Huawei>display  ip interface brief  View the interface summary 

[Huawei]display  this  Display the command configured at the current location 
[Huawei]display  current-configuration   View all instructions configured on this device 

6、 ... and 、DHCP service

– Dynamic Host Configuration Protocol Unified distribution management ip Address ;
Deploy one in the network DHCP The server , After that, the terminal device looks for DHCP Server acquisition ip address

Become DHCP Server conditions ：

1、 The device must have an interface or network card connected to the broadcast domain of the address to be dropped
2、 The interface or network card , You have to have legal ip Address , And can communicate

[Huawei]dhcp enable    Turn on the device first DHCP service 
 Create a device named xiaoqiang Of DHCP pond , Multiple ponds can be created on one device , But a pond can only serve one broadcast domain 
[Huawei]ip pool xiaoqiang
[Huawei-ip-pool-xiaoqiang]network 192.168.1.0 mask  255.255.255.0
[Huawei-ip-pool-xiaoqiang]gateway-list  192.168.1.1    default gateway 
[Huawei-ip-pool-xiaoqiang]dns-list  114.114.114.114 8.8.8.8  DNS  Server address 

[Huawei]interface GigabitEthernet 0/0/0
[Huawei-GigabitEthernet0/0/0]dhcp select global   Open on the interface of the lower address DHCP service 

7、 ... and 、 A term is used to explain

MTU：

Maximum transmission unit Default 1500 The data is processed in the upper three layers , In the future, it will go to the transport layer ; Need segmented data , The maximum capacity of each segment of data cannot exceed MTU value ; Segmentation is to allow multiple nodes to share bandwidth with little impact on each other ;
Port number ：0-65535 16 Bit binary structure
1-1023 Indicate port （ Static port ）– Mark various services on the server
1024-65535 Dynamic port （ High port ）– Mark the process of the terminal

UDP：

user datagram protocol – Non connection oriented unreliable transport protocol
Only the basic work of the transport layer is completed — piecewise 、 Port number

TCP：

Transmission control protocol – Connection oriented reliable transport protocol
Connection oriented ： Establish an end-to-end virtual link through three handshakes
Reliable transmission ：4 A reliable transmission mechanism – confirm 、 Sort 、 Retransmission 、 Flow control （ The sliding window ）
After completing the basic work of the transport layer , It also needs additional guarantee for transmission reliability ;

IPV4 Headlines ：

ARP： Address resolution protocol

positive ARP：

The target of the same network segment is known ip Address , But the unknown target mac Address ; Get the bet on the radio mac
Address

reverse ARP：

1、 Known opposite end MAC, Get the end-to-end ip Address ;

2、 Known local MAC Address , adopt
ARP Local query based on peer-to-peer query ip Address ;

Without any reason ARP：

Go forward ARP Inquire about , But the queried address is local ip Address ;– Address conflict detection

DNS：

Domain name resolution service , Known domain name for ip Address the query

encapsulation ：

Data processing from high level to low level , In the process, the data packet gradually increases

decapsulation ：

Data recognition process from low level to high level ;

flooding ：

The switch is an unknown target mac Address , The behavior of copying all interfaces of data frames

radio broadcast ：

Force the switch to flood , Finally, a local packet is forwarded to all nodes in the broadcast domain ;

PDU：

Protocol data unit , Mark the unit of each data package
The top three （ application 、 Express 、 conversation ）— The data packet
transmission -- paragraph
The network layer – package
Data link layer — frame
The physical layer — Bit stream

Half duplex ：

Data flow in a single point of time , There can only be one direction ; closed 、 Hair is done separately at different times

full duplex ：

Data sending and receiving can be carried out at the same time ;

TCP/IP（4 or 5） And OSI（7） The difference between ：

1、 The number of layers is different
2、3 Different layers ; TCP/IP Support only ip;OSI Support all network layer protocols ;
3、TCP/IP – Support cross layer encapsulation
Between routers and three-tier direct connected devices such as routers , Agreement for direct communication and dialogue , Can not be encapsulated 4 layer ;
In the layer 2 equipment room of the direct connected switch , You can directly access 2 layer , skip 3、4 layer ;– Speed up convergence
–OSPF/EIGRP/ICMP… Span 3 layer —STP… Span 2 layer

Cross layer to 3 When the layer , period 4 layer ; Then there will be 3 Layer header to complete 4 Layer work
— piecewise 、 Port number （ Distinguish between processes and services ）
IPV4 Data can be segmented in the header , Use protocol numbers to distinguish between processes and services

Cross layer encapsulation to 2 When the layer , period 3、4 layer ;
Ethernet, for example ：
The second generation Ethernet package is used by default , The package does not have the ability to slice ;
Therefore, cross layer packaging to 2 When the layer , You need to call the first generation Ethernet rules ;
The data link layer is divided into two sub layers ;LLC+MAC
LLC Logical link control sublayer — Responsible for segmentation and process differentiation
MAC Media access control sublayer — Control physical layer operation