Connectivity
Another key topic that the TCP/IP exam covers is connectivity. Here are some concepts you need to know about when you are completing the connectivity section of the TCP/IP exam.
RIP. RIP packets exchange routing information with other dynamic RIP routers. By default, an NT router cannot exchange RIP packets with other IP RIP routers unless you install RIP software and select the Enable IP Forwarding check box on the Routing tab of the TCP/IP Properties page.
Without RIP, you must use the ROUTE ADD command to manually set up router tables. The syntax for manual adds is
ROUTE ADD [destination net id] MASK [netmask] [gateway mask]
Multihomed host. You can use your NT server as a multihomed host, but each network card must have an individual IP address. A multihomed host is useful for hosting several Web sites.
Internet Information Server (IIS) and FTP. IIS serves primarily as a Web server, but it also supports FTP and Gopher. For an FTP client to access the services of an FTP server, the client must use the Windows Sockets interface to get to the session layer NetBT (NetBIOS over TCP/IP).
Internet Service Manager. ISM is a graphical administration tool. You can use ISM to centrally manage, control, and monitor the Internet services in your NT network.
Telnet. This protocol lets a computer become a dumb terminal on other hosts. When you connect to another host, you can access and run files and applications on that host. However, you can't download or upload files.
Remote Access Service (RAS). If you use a RAS server for dial-up networking, you must leave the default gateway information blank. The Internet Service Provider (ISP) will provide this information.
Monitoring and Optimization
The key to this section of the TCP/IP exam is how to monitor and make changes (via the Registry Editor, regedt32.exe) to optimize your network. You can use three monitoring tools to collect, view, and analyze information about your network:
Event Log. The Event Log in NT stores all critical system messages, not just those related to TCP/IP. You can use this log to track events and errors.
Network Monitor. The Network Monitor captures incoming and outgoing packets to help you detect and analyze problems. The monitor includes filters that limit what you view so the data doesn't become overwhelming. Commonly used filters are Filter during capture and Filter during display.
One area in Network Monitor that often confuses users is the monitor's range of service. With NT Server 4.0's Network Monitor, you can monitor only the specific system on which you install it. Users sometime believe that it can monitor other systems on the network.
Performance Monitor. The Performance Monitor (Perfmon) is NT's all-around tool for monitoring. It collects statistical measurements on hardware and software components. Perfmon establishes baselines from which you can judge those components' performance. You can then analyze performance to identify problems and opportunities for improvement. For Perfmon to collect TCP/IP information, you must install SNMP.
Troubleshooting
TCP/IP problems in NT 4.0 typically fall into two categories: configuration and name resolution. Configuration problems usually involve incorrect subnet masks, IP addresses, and default gateway addresses. You can use several tools to troubleshoot configuration problems.
Address Resolution Protocol. ARP displays the ARP cache, which contains media access control addresses. ARP also displays the NetBIOS cache, which contains resolved NetBIOS names.
Ipconfig. As the name implies, ipconfig shows the IP configuration information for the host. The ipconfig /all command will show not only TCP/IP configuration, but also DNS, WINS, DHCP, and NetBIOS information.
Netstat. This tool gives all the TCP/IP protocol statistics. Netstat also lets you know about the current state of TCP/IP connections.
Nslookup. This troubleshooting tool shows DNS server entry information. You can use nslookup to query a name server to determine whether it is working correctly.
Ping. You can use this utility with IP addresses or host names to verify connectivity with another host. You can also use ping to verify that your host is responding properly. When you use ping with the loopback address, you are testing only the IP layer and not the physical layer.
Route. With route print, you can view the routing table. With route add, you can add entries.
Tracert. This tool is similar to the ping utility. However, tracert traces only the route being taken.
You can easily troubleshoot name resolution problems with the ping utility. If you can ping a host using its IP address but not its host name, you have a resolution problem. (If you cannot ping the host at all, the problem lies elsewhere.) Here are five common causes of name resolution problems and how to prevent or fix them.
- You misspell the host name: Examine the HOSTS or LMHOSTS file to verify that you spelled the host name correctly.
- Comment characters prevent NT from reading the host name: Verify that a pound sign is not at the beginning of the line or anywhere on the line before the host name.
- The file contains duplicate host names: Verify that all host names are unique. When you have duplicate host names, NT will read only the first entry because it reads files linearly.
- NT contacts the wrong host: Verify that the IP address you entered in the file is valid and corresponds to the host name.
- You place an entry in the wrong file: Although similar, HOSTS and LMHOSTS files aren't interchangeable. HOSTS files map IP addresses to host names, and LMHOSTS files map NetBIOS names to IP addresses. If you put HOSTS entries in to the LMHOSTS file, NT will ignore those HOSTS entries. Similarly, if you put LMHOSTS entries in the HOSTS file, NT will ignore those LMHOSTS entries.
In addition to ping, useful name resolution utilities include nbtstat and hostname. The nbtstat utility (NetBIOS over TCP/IP) displays protocol statistics and current TCP/IP connections. This utility is useful for troubleshooting NetBIOS name resolution problems and has several parameters and options:
- -a(adapter status), which lists the remote machine's name table given its name
- -A(Adapter status), which lists the remote machine's name table given its IP address
- -c(cache), which lists the remote name cache, including the IP addresses
- -n(names), which lists local NetBIOS names
- -r(resolved), which lists names resolved by broadcast and via WINS
- -R(Reload), which purges and reloads the remote cache name table
- -S(Sessions), which lists the sessions table with the destination IP addresses
- -s(sessions), which lists the sessions table converting destination IP addresses to host names via the hosts file
The hostname.exe utility returns the name of the local host. You can use this utility only to view the name; you can't use it to change the name. You can change the host name from the Network Control Panel applet.
Ace the Exam
Although real-world, hands-on experience is the best preparation for the TCP/IP exam, knowing what to expect on the exam can be helpful. But you can't just memorize the concepts in these five sections to pass the exam. Rather, you must understand the reasoning behind these concepts. If you possess this understanding, you will have no trouble acing the TCP/IP exam.
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