Ethereum writing
Publish: 2021-03-26 01:57:36
1. Eth interface refers to the interface, is the most widely used LAN communication mode, but also a protocol. Ethernet interface is the port of network data connection
each version of Ethernet has a maximum cable length limit (that is, the length without amplification). Signals within this range can propagate normally, and signals beyond this range cannot propagate
in order to allow the construction of a larger network, repeaters can be used to connect multiple cables. Repeater is a physical layer device, which can receive, amplify and retransmit signals in two directions
extended data
several common Ethernet interface types
1. SC optical fiber interface
SC optical fiber interface has been applied in the era of 100base TX Ethernet, so it was called 100base FX at that time (F is the abbreviation of optical fiber). However, at that time, because the performance was not more prominent than twisted pair, but the cost was higher, so it was not popularized. Now the instry vigorously promotes gigabit network, and SC optical fiber interface is re valued
2. RJ-45 interface
this kind of interface is the most common network equipment interface, commonly known as "crystal head", and the professional term is RJ-45 connector, which belongs to the type of twisted pair Ethernet interface. RJ-45 plug can only be inserted along the fixed direction, and a plastic spring piece is set to be stuck with RJ-45 slot to prevent it from falling off
3. FDDI interface
FDDI has the highest transmission rate among the mature LAN technologies. It has the characteristics of timed token protocol, supports a variety of topologies, and its transmission medium is optical fiber. Fiber distributed data interface (FDDI) is a set of protocols developed by American National Organization for Standardization (ANSI) to transmit digital signals on optical cables
reference source: Network Ethernet interface
each version of Ethernet has a maximum cable length limit (that is, the length without amplification). Signals within this range can propagate normally, and signals beyond this range cannot propagate
in order to allow the construction of a larger network, repeaters can be used to connect multiple cables. Repeater is a physical layer device, which can receive, amplify and retransmit signals in two directions
extended data
several common Ethernet interface types
1. SC optical fiber interface
SC optical fiber interface has been applied in the era of 100base TX Ethernet, so it was called 100base FX at that time (F is the abbreviation of optical fiber). However, at that time, because the performance was not more prominent than twisted pair, but the cost was higher, so it was not popularized. Now the instry vigorously promotes gigabit network, and SC optical fiber interface is re valued
2. RJ-45 interface
this kind of interface is the most common network equipment interface, commonly known as "crystal head", and the professional term is RJ-45 connector, which belongs to the type of twisted pair Ethernet interface. RJ-45 plug can only be inserted along the fixed direction, and a plastic spring piece is set to be stuck with RJ-45 slot to prevent it from falling off
3. FDDI interface
FDDI has the highest transmission rate among the mature LAN technologies. It has the characteristics of timed token protocol, supports a variety of topologies, and its transmission medium is optical fiber. Fiber distributed data interface (FDDI) is a set of protocols developed by American National Organization for Standardization (ANSI) to transmit digital signals on optical cables
reference source: Network Ethernet interface
2. In recent years, Cisco's high-end routers have basically adopted IOS XR system instead of the original IOS system; The original IOS system has a variety of simulators to simulate, a variety of play; However, it seems that there are not many options for IOS XR simulation. You can download the IOS xrv-k9-demo-5.2.0 file (the version is not necessarily 5.2.0) from the Cisco official website, and use VMware to run and simulate the IOS XR system
however, when I first used it, I encountered a problem, that is, the router simulated by IOS XR only has two physical interfaces: mgmteth0 / 0 / cpu0 / 0, and gigabitethernet 0 / 0 / 0 / 0, which is obviously not enough to play
therefore, under VMware, add the [network adapter] of the virtual machine. No matter how much you add it, the number of physical interfaces in the IOS XR system is always the same. What can you do
the solution is as follows: IOS XR virtual machine in my document, under the corresponding folder, there is a file: xxxxx.vmx, which corresponds to the name of the virtual machine. Use WordPad to open (Note: do not use Notepad to open and edit, because this will cause an error to be reported when running the virtual machine at last, and prompt "dictionary error"). In this document, there are some information about IOS XR physical interface, such as:
Ethernet0. Present = & quot; TRUE"< br />ethernet0.virtualDev = " e1000"< br />ethernet0.connectionType = " bridged"< br />ethernet0.startConnected = " TRUE"< br />ethernet0.addressType = " generated"< br />ethernet0.generatedAddress = " 00:0c:29:1c:1d:34"
in this document, the number of Ethernet is consistent with the number of network adapters in the virtual machine. According to the MAC address of each Ethernet in the document, it can correspond to each network adapter in the virtual machine. Therefore, as long as the [network adapter] of the virtual machine is added, the number of Ethernet in this document will be increased, and the corresponding configuration will be added
however, the problem to be solved in this paper is rooted in a command: Ethernet0. Virtualdev = & quot; e1000"， By default, this command is available for Ethernet 0 and Ethernet 1, but not for other physical interfaces such as Ethernet 2 and Ethernet 3. Therefore, the router virtualized by IOS XR has no corresponding physical interface. By adding the following commands, we can solve the problem of unable to add physical interface of Router:
Ethernet 2. Virtualdev = & quot; e1000"< br />ethernet3.virtualDev = " e1000"
you can add [network adapter] in the virtual machine according to your own test needs, and add the above command in the VMX file, save the document, open it again, and you can see that the physical interface of the IOS XR router has increased, As follows
RP / 0 / 0 / cpu0: XR? Sho IP int bri
Thu Jul 16 22:45:55.638 UTC
interface IP address status protocol
mgmteth0 / 0 / cpu0 / 0 unassigned shutdown down
gigabitethernet 0 / 0 / 0 unassigned up
gigabitethernet ET0 / 0 / 0 / 1 unassigned shutdown down
gigabitethernet 0 / 0 / 0 / 2 unassigned shutdown down
gigabitethernet 0 / 0 / 0 / 3 unassigned shutdown down
note that when modifying the VMX document, you need to close the virtual machine first, save the closed document, and then open the virtual machine
when IOS XR virtual machine is just started, it is relatively slow, and it takes a long time to load the configuration, and the previous configuration can not be saved. As long as you wait for a period of time, you can resume normal use.
however, when I first used it, I encountered a problem, that is, the router simulated by IOS XR only has two physical interfaces: mgmteth0 / 0 / cpu0 / 0, and gigabitethernet 0 / 0 / 0 / 0, which is obviously not enough to play
therefore, under VMware, add the [network adapter] of the virtual machine. No matter how much you add it, the number of physical interfaces in the IOS XR system is always the same. What can you do
the solution is as follows: IOS XR virtual machine in my document, under the corresponding folder, there is a file: xxxxx.vmx, which corresponds to the name of the virtual machine. Use WordPad to open (Note: do not use Notepad to open and edit, because this will cause an error to be reported when running the virtual machine at last, and prompt "dictionary error"). In this document, there are some information about IOS XR physical interface, such as:
Ethernet0. Present = & quot; TRUE"< br />ethernet0.virtualDev = " e1000"< br />ethernet0.connectionType = " bridged"< br />ethernet0.startConnected = " TRUE"< br />ethernet0.addressType = " generated"< br />ethernet0.generatedAddress = " 00:0c:29:1c:1d:34"
in this document, the number of Ethernet is consistent with the number of network adapters in the virtual machine. According to the MAC address of each Ethernet in the document, it can correspond to each network adapter in the virtual machine. Therefore, as long as the [network adapter] of the virtual machine is added, the number of Ethernet in this document will be increased, and the corresponding configuration will be added
however, the problem to be solved in this paper is rooted in a command: Ethernet0. Virtualdev = & quot; e1000"， By default, this command is available for Ethernet 0 and Ethernet 1, but not for other physical interfaces such as Ethernet 2 and Ethernet 3. Therefore, the router virtualized by IOS XR has no corresponding physical interface. By adding the following commands, we can solve the problem of unable to add physical interface of Router:
Ethernet 2. Virtualdev = & quot; e1000"< br />ethernet3.virtualDev = " e1000"
you can add [network adapter] in the virtual machine according to your own test needs, and add the above command in the VMX file, save the document, open it again, and you can see that the physical interface of the IOS XR router has increased, As follows
RP / 0 / 0 / cpu0: XR? Sho IP int bri
Thu Jul 16 22:45:55.638 UTC
interface IP address status protocol
mgmteth0 / 0 / cpu0 / 0 unassigned shutdown down
gigabitethernet 0 / 0 / 0 unassigned up
gigabitethernet ET0 / 0 / 0 / 1 unassigned shutdown down
gigabitethernet 0 / 0 / 0 / 2 unassigned shutdown down
gigabitethernet 0 / 0 / 0 / 3 unassigned shutdown down
note that when modifying the VMX document, you need to close the virtual machine first, save the closed document, and then open the virtual machine
when IOS XR virtual machine is just started, it is relatively slow, and it takes a long time to load the configuration, and the previous configuration can not be saved. As long as you wait for a period of time, you can resume normal use.
3.
Recently, a photo of Chinese aunts posing at the blockchain conference became popular in the circle of friends, and netizens commented that aunts have been targeted by blockchain. Since the beginning of this year, some illegal elements have carried out pyramid selling activities under the banner of blockchain finance, becoming one of the latest varieties of pyramid selling. Recently, Xi'an City cracked a block chain pyramid selling case
Zhang Yangqiu said that virtual currency, as a new thing, is often used to engage in illegal and criminal activities. It usually controls a small number of indivial or company accounts to absorb and transfer funds, and establishes a pyramid selling network through the Internet to expand the scale of fund-raising. It is difficult for ordinary investors to see the operation rules behind it. She reminded that various virtual currency platforms generally publicize technologies such as "blockchain" and "decentralization", and some of them are also named after international organizations and multinational financial groups, which is extremely confusing. Middle aged and old people must be cautious in investment, and it is better not to set foot in unfamiliar investment fieldscontent source: Xinhuanet
4. On the one hand, the value of bitcoin comes from the objective resources and labor invested by people, such as computing power, applications, etc; Similarly, the value of bitcoin also comes from people's subjective identification. At least there are a group of people in the world who agree with the value of bitcoin and are willing to pay their own price to get it or simply invest in its world
the hypothesis of rational man in economics blinds many people. Because both indivials and people will fall into irrationality, especially in the financial market. This is the root of the birth of the financial bubble. People enter the irrational state because of their advantages and disadvantages. They are constantly changing from calm to happy, excitement, panic, anxiety and calm. So we also see the great fluctuation of bitcoin exchange rate, which is too normal for a brand new technological revolution and social concept revolution. What we should see is how it can always be reborn in the extreme. Br />
when we see bitcoin bubble, if we can not be deceived by the appearance of bubbles, we can see the real utility of bitcoin, with no reality whatever. The centralization of bitcoin brings high credibility, scarcity, value storage, the elimination of multiple payments, low transaction costs and breaking through the global trade protection barriers. It has already solidify the value foundation of bitcoin, which determines that bitcoin will not be just a bubble with no reality whatever.
there is no perfection in the world, everything is relative. Bitcoin still has some limitations, such as the loss of convenience e to security (slow confirmation time of transaction on the chain), for example, the arms race of computing power leads to the concentration of computing power to increase the 51% attack probability of the mine pool. The former can be realized by off chain transactions provided by enterprises with high reputation formed by fierce market competition, while the latter can be avoided by people who understand the concept of bitcoin actively seeking community cooperation. For example, the computing power of ghash.io mine was once as high as 40% a few days ago. We all told each other on the Internet that we hoped that the miners would take the initiative to stay away from ghash.io mine for a while. The mine itself also limited the further growth of computing power and evacuated the computing power to other mines to resolve the possible 51% attack. Bitcoin, a self-organized distributed ecosystem, has great vitality. Even if there are great problems in the future, I believe the community will graally find solutions. It's up to people. Compared with the current undercurrent of the failed legal currency system, bitcoin is obviously much more reliable, but not everyone can see the disadvantages of the legal currency system: mountain of debt, self righteous government that arbitrarily disrupts market behavior, high inflation sword, wide gap between the rich and the poor, declining proction efficiency
2013 is undoubtedly a brilliant year for bitcoin, because bitcoin began to go out of the geek circle and integrate into the social ecology.
the hypothesis of rational man in economics blinds many people. Because both indivials and people will fall into irrationality, especially in the financial market. This is the root of the birth of the financial bubble. People enter the irrational state because of their advantages and disadvantages. They are constantly changing from calm to happy, excitement, panic, anxiety and calm. So we also see the great fluctuation of bitcoin exchange rate, which is too normal for a brand new technological revolution and social concept revolution. What we should see is how it can always be reborn in the extreme. Br />
when we see bitcoin bubble, if we can not be deceived by the appearance of bubbles, we can see the real utility of bitcoin, with no reality whatever. The centralization of bitcoin brings high credibility, scarcity, value storage, the elimination of multiple payments, low transaction costs and breaking through the global trade protection barriers. It has already solidify the value foundation of bitcoin, which determines that bitcoin will not be just a bubble with no reality whatever.
there is no perfection in the world, everything is relative. Bitcoin still has some limitations, such as the loss of convenience e to security (slow confirmation time of transaction on the chain), for example, the arms race of computing power leads to the concentration of computing power to increase the 51% attack probability of the mine pool. The former can be realized by off chain transactions provided by enterprises with high reputation formed by fierce market competition, while the latter can be avoided by people who understand the concept of bitcoin actively seeking community cooperation. For example, the computing power of ghash.io mine was once as high as 40% a few days ago. We all told each other on the Internet that we hoped that the miners would take the initiative to stay away from ghash.io mine for a while. The mine itself also limited the further growth of computing power and evacuated the computing power to other mines to resolve the possible 51% attack. Bitcoin, a self-organized distributed ecosystem, has great vitality. Even if there are great problems in the future, I believe the community will graally find solutions. It's up to people. Compared with the current undercurrent of the failed legal currency system, bitcoin is obviously much more reliable, but not everyone can see the disadvantages of the legal currency system: mountain of debt, self righteous government that arbitrarily disrupts market behavior, high inflation sword, wide gap between the rich and the poor, declining proction efficiency
2013 is undoubtedly a brilliant year for bitcoin, because bitcoin began to go out of the geek circle and integrate into the social ecology.
5. 1. First of all, bitcoin is digital currency, code and data; Gold is a material object and a metal
2. Bitcoin was born in 2008 and has been known for more than 10 years; Gold originated from the feudal dynasty, with a history of thousands of years and a strong consensus
3. There are only 21 million bitcoins. The total amount of bitcoins is constant and will never be issued again. The mining cycle is halved every four years, which is deflationary; Gold needs physical mining, and the total amount of gold will change with the continuous mining
4. Bitcoin has the value of saving, and gold has the value of collecting
5. Bitcoin is divisible. One bitcoin can be divided into innumerable parts, up to 8 decimal places; Gold can not be subdivided, and the cost of segmentation is high and inconvenient
6. Bitcoin is more convenient to save assets. As long as you keep your private key, you can keep your wealth in your hands all the time; Gold cannot be stored in large quantities and needs to be stored in third-party institutions. It is clear how many asset centralization institutions there are.
2. Bitcoin was born in 2008 and has been known for more than 10 years; Gold originated from the feudal dynasty, with a history of thousands of years and a strong consensus
3. There are only 21 million bitcoins. The total amount of bitcoins is constant and will never be issued again. The mining cycle is halved every four years, which is deflationary; Gold needs physical mining, and the total amount of gold will change with the continuous mining
4. Bitcoin has the value of saving, and gold has the value of collecting
5. Bitcoin is divisible. One bitcoin can be divided into innumerable parts, up to 8 decimal places; Gold can not be subdivided, and the cost of segmentation is high and inconvenient
6. Bitcoin is more convenient to save assets. As long as you keep your private key, you can keep your wealth in your hands all the time; Gold cannot be stored in large quantities and needs to be stored in third-party institutions. It is clear how many asset centralization institutions there are.
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