Lan uses a Unified IP address to access the internet

Two days ago, the LAN was changed to a uniform mac problem and there was a conflict with the classical spicy M °.
The reason is that the unified mac will affect network work.

The classical idea of M ° is to change it to the same mac address without affecting the machine's Internet access.
I think the mac address is modified, and the switching environment is damaged. How can I connect to the Internet?

As we all know, switches work on ISO data connections.
After the network data passes down from the upper layer to the network layer, it is encapsulated as an IP packet. At this layer, only the IP address is known for transmission. When it reaches the data link layer, it is encapsulated as a data frame. At this layer, only the MAC address is known. In the exchange environment, data is transmitted by MAC. The working principle of a vswitch is also known. Every port of a vswitch has a learning function. Remember the MAC address of the NIC connected to the port, and then there is a data transmission requirement, it intelligently establishes a dedicated transmission channel, separates the conflict domains, and ensures data security to a certain extent.

But how can I access the same MAC address.

So I did a test:
A (192.168.30.1), B (192.168.30.2), C (192.168.30.3), and 3 computers.
The MAC address of A and B is changed to the same.
At this time, of course, A cannot access B. Because A accesses B's data, in the vswitch, it cannot accurately determine the target port by using the world's only MAC! Because their addresses are the same, it reminds me of Cisco's single-arm routing. However, this is just A hypothesis. If you want to confirm, the data sent by A is immediately transferred back to the same MAC as B, or to forward data frames to all ports (including their own) with the same MAC as B, it is best to use sniffing to determine. In addition, the vswitch does not tell you how to handle the same MAC.

After all, the generation of a vswitch is based on the unique MAC address.
In short, access between A and B fails. I'm sure. Neither network neighbors nor PING nor other application-layer software can access each other.


Conclusion 1: machines with the same MAC on the LAN cannot access each other.


Now let's talk about C. His MAC address is different from that of A and B until now it seems that he has not been affected.
Now PING machine A from C:
D: Documents and SettingsAdministrator> PING 192.168.30.1-t

Pinging 192.168.30.1 with 32 bytes of data:

Request timed out.
Request timed out.
Request timed out.
Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
Request timed out.

It seems that C cannot successfully ping.
PING machine B with C,
D: Documents and SettingsAdministrator> PING 192.168.30.2

Pinging 192.168.30.2 with 32 bytes of data:

Request timed out.
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Same. Machine A and machine B have some changes in the LAN ......


Conclusion 2: machines with no MAC modification and a unique MAC remain in the LAN. There are a lot of random obstacles when accessing machines with a duplicate MAC.


A and B cannot access each other ,:(.
Can I access C? Although A uses the same MAC address as B, in the exchange environment, it is clearly contrary to the transmission rules, but the test continues...
First, PING the host C that has not modified the MAC on server:
D: Documents and SettingsAdministrator> PING 192.168.30.3

Pinging 192.168.30.2 with 32 bytes of data:

Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
Reply from 210.72.28.253: bytes = 32 time <10 ms TTL = 64
............ Good condition
PING machine C on machine B:
The result is the same as above ..
This is not difficult. C does not modify the MAC. The switch can only pass through and send data to C through only one port.


Conclusion 3: machines with the same MAC in the LAN are not affected when accessing machines with no MAC modification.


I have never met these questions before. I know who is idle and will change it to the same MAC. I am so confused with my local network ......
Next, I went to test the connection to the INTERNET. I absolutely didn't agree that I can access the INTERNET in the Classical Style M °. The example just showed that I changed it to the same MAC address, it affects switch operations. Conclusion 2: This is explained.
Open your browser with machine A and enter HACKBASE. COM/BBS/INDEX. PHP ...... Open, nose, sweat!
Machine B, hurry up, enter the address you are used ,! $ ###^ @ # $ % # ^: The network speed is as fast and depressing as it is in normal time.
Machine C should be okay. After all, it is the only MAC machine in the world ,...... Sure enough. I opened the website quickly.
...... Machine A and machine B have the same MAC. In A LAN, they can access the Internet at the same time, and even open different web pages without notice of stagnation.
By changing the URL, you can quickly open the chat software .......
I still remember conclusion 2: "There is no MAC modification in the LAN and there are a lot of random obstacles when accessing a machine that is changed to a duplicate MAC,

I did not PING my conclusion in a few minutes, but I did PING and watched for nearly 40 minutes...
How can a lan gateway send the results returned by the WEB server to A and B ????
I tried IE, FTP, and QQ ...... Very fast indeed.
The reason is described later.

Conclusion 4: machines with the same MAC address can access the INTERNET at the same time on the LAN.

If you know what is going on, of course you are not depressed.
But I am depressed. I don't know why the gateway does not make any error when sending the INTERNET Data Request results back to machines A and B? How accurate is it when a vswitch is used? Their

MAC is the same ..
So I did this test. First, I used machine C to PING machine. The results are poor. As described in conclusion 2, ICMP messages return very few, but occasionally a REPLY is returned.
At this time, I ran to machine A and pinged machine C on machine A. Of course this can be good. All the ECHO results are REPLY and can be pinged.
At this time, the result of machine C has changed, and the result of machine C's PING to machine A has also changed to that of all machines that can be pinged.
I opened a new CMD window on C. I can PING machine B without pinging.
At this time, I ran to machine B, input the PING machine C-t, and then looked at machine C. I can also PING machine B. The effect is acceptable.
Note: The ping I just used adds-t. This allows continuous PING.
Now I ran to machine A and ended the command to PING machine C.
...... The results on machine C have changed, and A large number of timeout occurs when the PING to A is returned.
The preceding actions are repeated several times. It is concluded that:


Conclusion 5: when changing to a uniform MAC machine and proposing a Communication Request to a machine without changing the MAC, the switch remembers to change the request to the port of the uniform MAC machine, then, if the MAC server is not changed, you can send the result data to the requesting server through the port of the switch.
This is why conclusion 4: the LAN gateway can return the data returned by the INTERNET server to the machine on the LAN for MAC modification.


I started to think that machines on the same MAC could access the INTERNET. It was strange that after knowing the reason, I felt that it was normal and I had a new understanding of the switch.
Now I want to restore my network. I don't need to use so many duplicate MAC addresses, because LAN Operations won't work.
First, I deleted the set IP address, but the machines quickly obtained a new IP address from the still running DHCP server !!
The IP addresses are the same !~~ This is because MAC is the same. DHCP assigns an IP address to the host by assigning a different IP address to each MAC.
It is not surprising that machines A and B are assigned the same IP address at the same time because they both have the same MAC address ..
But ...... I found that there was no prompt of IP conflict when they were assigned the same IP address. This is something I did not expect. Haha.
I'm glad that I didn't forget to test their online functions.
! ￥ ...... %! ￥ %! · # % They can access the Internet .!!! This time I am truly dizzy.
When a machine with the same MAC address and IP address sends an Internet request, the switch remembers the corresponding port and sends it back according to the original port when data is returned.

The machine still received the data .!!!
Information Transmission is fast. Once the data is sent back, it will be done in an instant!


Conclusion 6: if a machine with the same MAC address is set to the same IP address, no IP address conflict error is reported. You can still access the internet !!



Haha, it's funny. This configuration is meaningless.
I did this for gambling, entertainment, and INTERNET access by machines on the LAN with the same IP address and MAC.
This message is good.
We all know that ADSL Broadband can be used to connect to a small-sized home LAN and share the Internet.
However, after that, the BT device was confusing, and he blocked Internet sharing.
Network Vanguard, with the filtering and detection function, can capture whether the data packet that flows through contains multiple IP addresses and MAC addresses. It can detect whether a user has installed a proxy and NAT device for further determination.

Whether a shared network exists.
I suppose that in my family, if there are few computers in the family, I can modify the uniform MAC, configure the uniform IP address, and connect to ADSL to access the Internet. How can I check the network Vanguard?

Finally:
All of the above are done when the number of machines with a uniform MAC address and a uniform IP address is small. If there are many machines, there will be problems accessing the Internet.
It is very likely that, among the results returned by a switch to a machine, other unified MAC and IP machines send Internet requests. In this case, in an instant, the switch does not know that the packet should be returned to that port, because they have the same MAC address, so he is dizzy ...... But fortunately, our applications are generally dominated by TCP. If packet loss is found, the machine will ask for one more time to the INTERNET. Therefore, the network application can be maintained as long as the packet loss occurs. Even for udp qq, it is also because the switch processes packets instantly.

Speed, can work well! But I don't know.