There are many techniques to troubleshoot wired and wireless network problems. Connection speed and strength, problems in the NIC, and access problems are a few of the issues you will learn to troubleshoot in this lesson.
After completing this lesson, you should be able to:
Identify tools, diagnostic procedures, and techniques for troubleshooting networks
Wireless Connection Speed and Strength
Troubleshooting a NIC
To configure a NIC on a Windows XP computer, attach the NIC to any available PCI slot on the motherboard and install the appropriate network card drivers using the Device Manager.
You should connect the NIC to a hub or a switch by using a patch cable. A patch cable is a UTP cable used to connect two devices on a network. A patch cable can be a crossed cable or a straight cable. If you're connecting similar devices, such as two computers, you should use a crossed patch cable. If you're connecting dissimilar devices, such as a computer and a hub or switch, you should use a straight patch cable.
To troubleshoot NIC problems, make sure the network patch cable is plugged into the wall socket and the computer's NIC. You can check the cable itself with a LAN tester tool or by replacing the cable.
Use Device Manager to check the status of a NIC. Device Manager is used to install device drivers and verify that a device is functioning properly.
To troubleshoot NIC problems, you should check to see whether the link lights are present on a network card.
To verify that the NIC is working properly on a computer, use a loopback device.
Troubleshooting Internet Access Problems
To troubleshoot Internet access problems you should check whether the NIC is configured properly. You should check the DNS, DHCP, and default gateway settings to troubleshoot Internet access problems.
DNS
DNS is a distributed addressing system that resolves a domain name into its numeric IP address. DNS allows you to use the Internet without the need to remember long lists of cryptic numbers. Each domain is an independent namespace that corresponds to a particular organization, and DNS servers manage requests for information regarding the IP addresses of particular DNS domains.
To configure DNS on a client computer, specify the DNS address provided by your ISP. The procedure involves the following steps:
Step Action
1 Open TCP/IP Properties from the Local Area Connection Properties dialog box.
2 In the General tab of the TCP/IP Properties dialog box, enter the DNS server's IP address in the Preferred DNS Server field.
Note:
If you are able to PING to a public IP address but are not able to PING the same IP address by using a Fully Qualified Domain Name (FQDN), you should verify the DNS IP settings.
DHCP
DHCP is a protocol that dynamically delivers IP address configuration information from a central server. DHCP automatically assigns the IP address, subnet mask, and DNS server address to the client computers. A DHCP client performs the following tasks to configure TCP/IP addresses:
Step Action
1 The client starts and enables TCP/IP.
2 The client discovers that configuration of TCP/IP is set to automatic. The TCP/IP stack sends a DHCPDISCOVER packet to request configuration parameters from a DHCP server.
3 Each DHCP server on the network responds with a DHCPOFFER packet, which contains an IP address the client can use.
4 The client accepts the first DHCPOFFER packet it receives and configures itself with that IP address.
5 The client sends a DHCPREQUEST packet to the DHCP server to accept the IP address. Clients that decline DHCPOFFER packets send DHCPDECLINE packets to the appropriate servers.
6 The DHCP server responds with a positive acknowledgement, known as a DHCPACK packet, if the IP address is unique on the network. If the DHCP server discovers an IP address conflict, it responds with a negative acknowledgement, known as a DHCPNACK packet. The DHCPNACK packet revokes the IP address and forces the client to send a new request for an IP address.
7 The client can use the IP address for a limited time, known as the address lease period. When half of the lease time expires, the client will request another address.
Network Devices
There are a number of things you can do to increase the performance of a network. Upgrade slow networks by using faster devices to connect to the network is one of them.
Let's look at some of these devices.
Bridges
In the past, bridges were used to connect two different network segments in a LAN and increase the performance of a network. Bridges operated at the data link layer of the Open System Interconnect (OSI) model. But bridges have become obsolete and are not used today.
Switches
Switches have replaced hubs, because switches provide faster transmission speeds. If you are using hubs your network performance might be slower than it could be, and it's better to use switches. Switches operate at the data link layer of the OSI model.
Router
A router is a networking device used to forward IP packets to a host on a different network. The process is known as routing. Routers operate at the network layer of the OSI model.
MAC Address
A MAC address is the 48-bit physical address of a NIC. This is a unique address assigned to the NIC by the vendor. To determine the MAC address of a computer, you can use the IPCONFIG /ALL command from the command prompt.
Status Indicators
You can check the status of network devices such as NICs or switches by looking at their status indicator lights. A NIC has two indicators: a link indicator and an activity indicator. If the NIC is not properly connected to the network, the link indicator or activity indicator may be off. If the NIC is properly connected to the network, the link status will be green. A blinking activity indicator shows that data is being sent and received over the network. An illuminated indicator light on a NIC card shows that the network cable is connected properly to another Ethernet connection.
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