Configuring and Troubleshooting Client Connectivity

Connecting clients to an existing network is a common task for network administrators. Connecting a client system requires establishing the physical connection, defining network protocols, assigning permissions, and accessing server services and resources. This section explores the requirements to connect a client PC to a network.

Verifying Client TCP/IP Configurations

Configuring a client for TCP/IP can be relatively complex, or it can be simple. Any complexity involved is related to the possible need to configure TCP/IP manually. The simplicity is related to the fact that TCP/IP configuration can occur automatically via DHCP or through APIPA. This section looks at some of the basic information required to make a system function on a network, using TCP/IP. At the least, a system needs an IP address and a subnet mask. The default gateway, DNS server, and WINS server are all optional, but network functionality is limited without them. The following list briefly explains the IP-related settings used to connect to a TCP/IP network:

• IP address-Each system must be assigned a unique IP address so that it can communicate on the network. Clients on a LAN will have a private IP address and matching subnet mask. Table below shows the private IP ranges. If a system has the wrong IP or subnet mask, that client system cannot communicate on the network. If the client system has an IP address in the 169.254.0.0 range, the system is not connected to a DHCP server and not getting on the network.
  
  Private Address Ranges

  Class	Address Ranges			Default Subnet Mask
  A	10.0.0.0-10.255.255.255		255.0.0.0
  B	172.16.0.0-172.31.255.255	255.255.0.0
  C	192.168.0.0-192.168.255.255	255.255.255.0
  

• Subnet mask-Enables the system to determine what portion of the IP address represents the network address and what portion represents the node address. Refer to Table above to see the right subnet mask associated with each private IP range. To be part of the network, each client system needs to have the correct subnet mask, and the subnet mask must use the matching one used with the rest of the network.
• Default gateway-Enables internal systems to communicate with systems on a remote network. In home use, the gateway would likely be the DSL or cable modem that acts as a router. In a business environment the gateway is the device that routes traffic from the workstation to the outside network. This network device will have an IP address assigned to it, and the client configuration must use this address as the default gateway. If not, the system cannot be routed outside the local network.
• DNS server addresses-Enable dynamic hostname resolution to be performed. It is common practice to have two DNS server addresses defined so that if one server becomes unavailable, the other can be used. The client system must be configured with the IP address of the local DNS server. If a client system has the wrong DNS address listed, hostname resolution will not be possible.

NOTE: TCP/IP Connection Requirements At a minimum, an IP address and a subnet mask are required to connect to a TCP/IP network. With just this minimum configuration, connectivity is limited to the local segment, and DNS resolution is not possible.

When manually configuring a system to use TCP/IP, all information needs to be entered into the respective dialog boxes carefully. Entering a duplicate IP address might prevent the client system from logging on to the network; the wrong gateway will prevent the system from accessing remote networks, and so on. To view the IP settings of a client system, many utilities are used, including the ipconfig command for Windows systems and the ifconfig for Linux and UNIX systems.

When troubleshooting a system, ensure that the IP address, default gateway, subnet mask, and DNS are correctly set. This information can be assigned using DHCP and should not have any errors; however, in networks where DHCP is not used and settings are inputted manually, these settings must be verified.

Setting Port Speeds and Duplex

When configuring a client for the network, you need to be aware of two more settings: port speeds and duplex settings. Adjust these two settings in Windows in the Network Properties area of the Windows operating system.

Several settings for port speed and duplex setting. These settings can be set to autoconfiguration to detect the setting used by the network. It can also be set to one of the other settings to match the network configuration-for example, 100Mbps and half duplex. If you work with a client system that cannot log on to a network, it might be necessary to ensure that the duplex setting and port speeds are correctly set for the network.