ADSL and HUB
ADSL is a high-speed broadband Internet access method that runs on the original telephone line. It has the advantages of saving investment, fast Internet access, and simple installation. Many LANs, especially Internet cafes, currently use this method. Of course, there are also many failures in this way to access the Internet. Let me talk about the troubleshooting methods and examples of ADSL failures for everyone.
Factors causing ADSL failure
Most of the common hardware failures of ADSL are problems such as loose connectors, broken network cables, damaged hubs, and computer system failures. Generally, you can help locate by observing the indicator light.
In addition, abnormal voltage, high temperature, and lightning strikes are also prone to failure. Where the voltage is unstable, the Modem should be equipped with a low-power UPS. The Modem should be kept dry and ventilated, avoid water, and keep clean. In case of thunderstorms, be sure to unplug the Modem power supply and all connections. Modem is damaged. If the indicator is off, or only one light is on, or the 10Base-T light is still off after replacing the network cable or network card, the modem is damaged.
The long distance of the line, poor line quality, and unreasonable connection are also reasons why ADSL cannot be used normally. Its performance is often lost synchronization, synchronization difficulties or consistency is very slow. The solution is to put the equipment that needs to be connected in parallel, such as telephone extensions, faxes, and ordinary Modems, into the PHONE port of the splitter: check whether all the connectors are in good contact, and the household lines with poor quality should be modified or replaced.
Basic method for locating ADSL faults
ADSL fault location requires some experience. The general principle is: pay attention to indicator lights and error messages, first hardware then software, first internal and then external, first local and then external network, first try the host and then check the customer, fully check and then declare. The declaration of faults should be accurate and concise, and try to correspond the problems encountered to the faults mentioned in the user manual. When reporting a fault to the equipment room, first report the port number and user name according to the user manual. For frequent failures, the user should record and mention them in the declaration.
1. Check whether the power indicator is normal
The power indicator is located on the far left of the user's Modem 3 indicators. If the power indicator is off, the user can solve the power problem by himself.
2. Whether the data indicator is normal
The data indicator is located on the right side of the three indicators of the user Modem. If the indicator lights continuously, it is normal, indicating that the line from the user terminal to the DSLAM central office is not faulty: if the indicator light is off, it indicates that there is a problem with the line. solve.
3. Whether the user changes the IP address by himself
Each user's PC has its fixed IP address. If the user changes its address, the telecommunications department can provide the IP address of its PC and change the IP address back.
4. Whether the user's network card and network cable are normal
After the user's PC network card is connected to the modem via the network cable, its indicator light will flash. If the indicator light does not flash normally, it indicates that the user's network card or network cable is faulty.
If all of the above are normal and the user still cannot access the Internet, it must be resolved on site by the technical staff of the ISP.
Fault diagnosis processing example
1. The computers on the LAN cannot use PPPoE
[Fault phenomenon]
An ADSL connection uses a 10 / 100Mb / s HUB, but computers on the local area network cannot use PPPoE.
[Fault analysis and processing]
ADSL uses the 10Base-T standard, which is 10Mb / s. It will be no problem to connect 10 / 100Mb / s HUB, but if the connection speed between the computer and HUB is 100Mb / s, HUB 10 / 100Mb / s exchange The module currently does not support PPPoE very well, so PPPoE may not be able to find the ADSL signal at 100Mb / s network speed and cannot be used. The solution is to use a 10Mb / s connection method for the computer for PPPoE dial-up to make a 10Mb / s network cable, or force the network card to work at 10Mb / s speed.
2. A crash occurs when the data flow is large
<[Fault phenomenon]
An ADSL will crash when the data traffic increases.
[Fault analysis and processing]
In general, this is caused by the quality or compatibility of the network card, especially the old ISA bus IOM network card. Because PPPoE is a relatively new technology, such network card compatibility may be problematic and the speed is slower. , Causing conflicts, and eventually the line locks up, or even crashes.
3. The startup speed becomes slow after installing PPPoE
[Fault phenomenon]
After installing the ADSL PPPoE software, the computer starts up slowly.
[Fault analysis and processing]
This is related to the problem with the network card settings. Since a legal IP is required when the system is started, the DHCP server needs to be correctly set in the LAN. If it is a stand-alone use, assign an IP to the network card to solve the problem, for example: 192.168.xxx.xxx Subnet mask: 255.255.255.0.
4. Cannot list ISP service items
[Fault phenomenon]
PPPoE software installation and work are normal, but can not list ISP service items.
[Fault analysis and processing]
First check whether the hardware connection is correct and whether the ISP is providing services. These can be judged by observing the display status of the ADSL Modem synchronous work light. If the synchronous work light shows normal operation, then check whether other equipment in the computer interferes with the work of ADSL. And upgrade the driver. Another point to note is whether the ISP has opened the corresponding service. Because ADSL has some special numbers bundled in the telephone exchange, the ISP needs to authenticate these numbers before it can be regarded as the user ’s line is legally available; and the ISP ’s ADSL access The server is not turned on, and it is impossible to list server items.
5. ADSL Internet speed is slow
[Fault phenomenon]
Sometimes ADSL access speed is not much faster than ordinary dial-up modem.
[Fault analysis and processing]
The main reasons for the slow access speed of ADSL are:
1) If you visit a foreign site, the visit will be affected by factors such as the export bandwidth and the configuration of the other site.
2) ADSL technology has high requirements on the quality of the telephone line, and the ADSL currently used is a kind of RADSL (rate adaptive ADSL). If the telephone line between the building where the telephone office is located and the user is interfered by external factors for a certain period of time , RADSL will dynamically adjust the user's access speed according to the quality of the line and the distance of the transmission distance.
6. Sometimes not connected to the internet
[Fault phenomenon]
ADSL sometimes can't get online normally.
[Fault analysis and processing]
ADSL is a technology based on twisted pair transmission. Twisted pair twists two insulated copper wires with each other according to a certain rule, which can effectively resist external electromagnetic field interference. Most of the telephone lines are parallel lines. The lines from the telephone company's junction box to the user's telephone are mostly parallel lines. This is very unfavorable for ADSL transmission. Excessively long non-twisted pair transmission will cause unstable connection and ADSL lamp flashing. Phenomenon, which affects the Internet. Because ADSL superimposes high-frequency digital signals on the low-frequency voice of ordinary telephone lines, the addition of any equipment in the connection from the telephone company to the ADSL filter will jeopardize the normal transmission of data, so do not connect in parallel before the filter Telephones, telephone immobilizers and other equipment.
7. The indicators of ADSL are normal but still off the network
[Fault phenomenon]
The indicator light of an ADSL is green, but there is also a disconnection phenomenon, and it is fine after restarting the Modem.
[Fault analysis and processing]
This situation often occurs on network users who do not have a proxy server, a firewall or a router. This is because there is a "lOBase-T" port on the ADSLModem. This port is the HUB port of the local area network. Although it is a 10Mb / s port, the upstream bandwidth of ADSL is only a few hundred kb / s. If the ADSL is directly connected to the HUB in the user's LAN, and the HUB is connected to the following client, many packets in the network that are not related to ADSL will occupy the ADSL upstream channel, and ADSL cannot control the broadcast storm in the LAN; if the ADSL upstream transmission capacity is exceeded , The data packet will be loaded into the ADSL buffer; if the data volume continues to increase, the buffer overflows, causing ADSL "sleep" phenomenon. Only restart the Modem. The solution is to be a proxy server with dual network cards, which can cut off the direct communication between the modem and the LAN, avoiding the above problems.
8. Virtual dialing fails
[Fault phenomenon]
ADSL prompts an error message when using virtual dialing software, and dialing fails.
[Fault analysis and processing]
If the dialing window displays "Begin NegoTIaTIon" and waits, finally the menu "TIme out" will pop up directly. The main reason is that the network cable on the 10Base-T port on ADSL is not connected or the ADSL network is not working. You can restart ADSL and try again.
If the dial window displays "Begin NegoTIation", then "Authenticating", and finally "Authentication Failed", this situation indicates that the user account or password is incorrect.
If the dialing window displays "Begin Negotiation", then "Authenticating", then "Receiving Network Parameter", and finally the menu "timeout" pops up. This situation indicates that the dialing IP address is already full and needs to be dialed later.
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