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segment) as defined by the subnet mask, the UPSLink will establish a direct connection. If the desired
TCP/IP host specified in the packet is not identified as belonging on the local network segment, a
connection is established through the given default gateway.
Default gateway
A gateway is a network point that acts as a portal to another network. This point is usually the
computer or computers that control traffic within a network or a local ISP (Internet service provider).
The UPSLink uses the IP address of the default gateway computer to communicate with hosts outside
the local network environment. Refer to the network administrator for a valid gateway IP address.
Primary and Secondary DNS
The DNS (Domain Name System) server is used to locate and translate the correct IP address for a
requested web site address. A domain name is the web address (i.e.
www.yahoo.com
) and is
usually easier to remember. The DNS server is the host that can translate such text-based domain
names into the numeric IP addresses for a TCP/IP connection.
The IP address of the DNS server must be able to access the host site with the provided domain
name. The UPSLink provides the ability to configure the required IP addresses of both the Primary
and Secondary DNS servers addresses. (The secondary DNS server is specified for use when the
primary DNS server is unavailable.)
4.1.2. Using DHCP
Dynamic Host Configuration Protocol (DHCP) is a communications protocol that lets network
administrators manage and automate the assignment of IP addresses centrally in an organization's
network. DHCP allows the network administrator the ability to supervise and distribute IP addresses
from a central point and automatically send a new IP address when a computer is plugged into a
different network location.
When in static IP mode, the IP address must be entered manually at each computer. If a
computer is moved to another network location, a new IP address must be assigned. DHCP allows all
the parameters, including the IP address, subnet mask, gateway and DNS servers to be automatically
configured when the IP address is assigned. DHCP uses a “lease” concept in assigning IP
addresses to a computer. It limits the amount of time a given IP address will be valid for a computer.
All the parameters required to assign an IP address are automatically configured on the DHCP server
side, and each DHCP client computer receives this information when the IP address is provided at its
boot-up.
Each time a computer is reset, the UPSLink broadcasts a DHCP request over the network. The
reply generated by the DHCP server contains the IP address, as well as the subnet mask, gateway
address, DNS servers and the “lease” time. The UPSLink immediately places this information in its
