|  | 8.6 | TCP/IP Fundamentals
| 8.6.9 | IP address, DNS, default gateway, IP proxy, WINS, DHCP, host name, and internet domain name
Normal configuration parameters for a workstation include: IP address and subnet mask, DNS setting, default gateway and subnet mask, IP Proxy, WINS, DHCP, host name, and Internet domain name. IP Address and Subnet Mask When assigning IP addresses, two important factors must be considered: the IP address needs to be unique and the IP address must be assigned a subnet mask. When a DHCP server assigns an IP address, it specifically assigns unique addresses to each device, not duplicating any address. If manually assigning IP addresses, it is important no two devices have the same IP address. Each address must also have a subnet mask to properly communicate with the network. The network and host ids of an IP address are determined by the subnet mask; therefore, it is important that each IP address has a subnet mask. DNS Setting Domain Name Services (DNS) is a name resolution service that resolves (associates) host names to IP addresses. DNS keeps a record of IP addresses and hosts names in a process called a domain. DNS provides services along a hierarchical chain, with a database design similar to a file tree structure (root-level/top-level/second-level/host name). DNS also services requests for host names that can not be resolved locally. Large internetworks have several levels of DNS servers to provide efficient name resolution. Default Gateway and Subnet Mask The interface of a router, which resides on a LAN, is called the default gateway. The default gateway is the location where all non-local network traffic that has no specific route to a destination is sent and the default gateway acts as an entry and exit point of a subnetwork. When sending data to a remote subnet, the host sends the packet to the initial router specified as its default gateway. The router receives the packet, then must determine whether the destination location is on its local networks or send the data to another router for delivery. IP Proxy A proxy server is a type of a "go-between" between the Internet and the users of a network. If a client needs information from the Internet, the proxy server searches for the destination and retrieves the information. This provides for higher security and faster service because the client, itself, does not directly connect to the destination. WINS Windows Internet Naming Service (WINS) works as DNS does to resolve IP addresses with host names. WINS uses a flat namespace by using NetBEUI, instead of using a hierarchical one like DNS. To resolve an IP address, WINS client hosts registers its NetBIOS and IP addresses with the WINS server, then the WINS client host sends a name query request to the WINS server, indicating that it desires to transmit to another host. If the desired IP address and host name are found in the server's WINS registry, then they will be sent to original WINS client host. Requests made by WINS are routable. The WINS proxy agent is used for non-WINS clients such as UNIX hosts; however, WINS does not provide support for Macintosh OS's. DHCP The Dynamic Host Configuration Protocol (DHCP) automatically distributes IP address settings to devices, which are connected to the network, when DHCP Server clients log on. When a client tries to connect to network, a request is sent to the DHCP server for configuration settings. Once the server receives the message, the DHCP server sends a reply to the client, which includes the configuration information, then keeps a record of the addresses that have been assigned. DHCP uses the BOOTP protocol to communicate with clients. Clients must renew their IP addresses after 50% of the address lease life, and again at 87.5% of the lease life, by sending a DHCPREQUEST message. Client hosts keep their IP address until their lease expires or they send a DHCPRELEASE command. IPCONFIG and WINIPCFG are utilities run from the command line that allow verification of the IP Address information that has been assigned to the client host. Host Name A host name is assigned by the network administrator to identify each device on the network. By default, on Windows-based machines, host names are the names of the computers. Internet Domain Name The Internet Domain Name is assigned by ARIN, a company that assigns all the domain names on the Internet. The domain name consists of two parts, the hostname and the domain. In the address www.cisco.com, the www is the host name and the cisco.com is the domain. Combined together, www.cisco.com becomes a fully qualified domain name (FQDN).