Remote connectivity errors are bugs that prevent you from connecting to the office network, from remotely dialing in to your home computer, or from logging on to your ISP and subsequently the Internet. Although many means and methods are available for establishing remote connectivity, network administrators can focus their attention on some common hot spots when troubleshooting errors, including authentication failure, protocol configuration problems, and physical connectivity. Troubleshooting Physical ConnectivityWhen you're troubleshooting remote connectivity errors, it is often easy to forget the most basic troubleshooting practices. By this, we mean ensuring that all the physical connections are in place. When you suspect a physical connectivity problem, here are a few key places to look:
Now that we have looked at some of the more generalized considerations of remote connectivity troubleshooting from a physical perspective, we'll focus specifically on some of the commonly used remote access technologies. DSLTroubleshooting DSL is similar to troubleshooting any other Internet connection. The following are a few things to check when users are experiencing problems with a DSL connection:
Cable Troubleshooting ProceduresIn general, cable Internet access is a low-maintenance system with very few problems. When problems do occur, you can try various troubleshooting measures:
If you are sure that the connectors are all in place and the configuration of the system is correct, the next step is to call the technical support line of the cable provider. Home Satellite Troubleshooting ProceduresYour ability to troubleshoot satellite Internet connections might be very limited. The hardware associated with home satellite remote access installations are very specialized, and equipment providers often prefer that you let them do the hardware troubleshooting. Given this limitation, calls to technical support occur very early in the troubleshooting process. Wireless Internet Access Troubleshooting ProceduresTroubleshooting wireless access is normally confined to ensuring that the adapter is functioning correctly and configured properly. The main factors that can affect wireless access are environmental conditions and outside interference. Many people who live in areas that often have fog or other damp conditions experience poor performance (or none at all) from wireless Internet service. Here are some specific things you should check when troubleshooting a wireless connection:
If you are sure that everything is configured correctly, you might have to contact the wireless provider to see if anything is amiss. POTS Troubleshooting ProceduresTroubleshooting a dial-up connection problem can be tricky and time-consuming because you must consider many variables. In fact, of the remote connectivity mechanisms discussed in this chapter, you are far more likely to have problems with a POTS connection than any of the others. The following are some places to start your troubleshooting under various conditions. If the user is unable to dial out, try the following:
If the user can dial out but can't get a connection, try the following:
If the user can dial out and can get a connection but is then disconnected, try the following:
Modem-Specific TroubleshootingIf you are confident that a modem is installed and configured correctly, but it's still not working properly, you can test and configure it by using special commands from the AT command set. Table 10.12 lists some of the most commonly used AT commands.
In general, getting the modem to respond to an ATZ command is a good enough indicator that the modem is functioning.
Troubleshooting Authentication FailureAll forms of remote connectivity should require some form of authentication to confirm that those trying to access the remote resources have permission to do so. As a network administrator, you can expect to become very familiar with authentication troubleshooting. Quite often, authentication errors result from users incorrectly entering usernames and/or passwords.
Authentication issues can also arise as a result of permissions changes in users' accounts. If you're troubleshooting remote connectivity and you have confirmed that the correct username and password are used, you should confirm that the user has the appropriate permissions to access the network. The third and perhaps least likely cause for authentication failure is a downed authentication server. In such a circumstance, you are likely to receive numerous calls regarding authentication difficultynot just one or two. Troubleshooting Protocol Configuration ProblemsMany, but not all, of the problems you encounter with remote connectivity can be addressed with the measures listed previously. However, you might encounter a problem when you have confirmed that the network user is using the correct username and password combination, that no changes have been made to the user's account information, that all physical connections are in place, and that the user still cannot establish a remote connection. The next most likely cause of a client connectivity problem is protocol configuration. Protocol configuration issues are usually on the client side of the network. On a TCP/IP network, each client computer must have a unique address in order to participate on the network. Failure to obtain addressing information automatically could indicate a problem with a DHCP server. You should check the DHCP server to make sure that it is functioning and that addresses are available for assignment. Beyond basic protocol issues such as addressing, remote connectivity troubleshooting also brings with it the additional considerations of authentication protocols. There is one basic rule that applies to all such issues. If a client in a remote connectivity solution is configured to use one type of authentication protocol, and the server to which he is connecting does not support that protocol, the connection will be refused.
Troubleshooting Small Office/Home Office RouterAs more people choose to use broadband Internet connectivity methods such as cable and DSL, the use of compact hub/router and switch/router combinations has become commonplace. Most SOHO routers are, in fact, more than routers. Most are also Ethernet hubs or switches, making it possible to share an Internet connection with other systems on the network. They also typically provide basic firewalling capabilities and, in many cases, DHCP server functionality. ConfigurationThe most common configuration method for SOHO routers is through a browser interface, though some models also use a custom application for this purpose. Configuration is generally straightforward, as SOHO routers are designed to be home user friendly. TroubleshootingBecause a SOHO router is a network device, the rules and procedures that apply to other troubleshooting scenarios are valid. If you are experiencing Internet connectivity issues on a network with a SOHO router, the first step is to ensure that the SOHO router is powered on and that all the network connections are complete and secure. Also, familiarize yourself with the diagnostic LEDs on your SOHO router so that you can interpret the information they provide accordingly.
One of the easiest ways to test whether the SOHO router is the cause of a problem is to remove it from the communications chain and plug a PC directly in to the broadband interface (be that cable or DSL). If the PC is configured to obtain an IP address automatically, it should be able to get an IP address from the ISP just as easily as it would from the SOHO router. If the system subsequently works fine and can access the Internet, you know that the problem lies with the SOHO router and not the configuration of the system.
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