NonStop S-Series Planning and Configuration Guide (G06.29+)

Terms and Concepts
HP NonStop S-Series Planning and Configuration Guide—523303-021
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IP Addresses
Domain Name Servers
Every domain is served by a domain name server. A domain name server takes host
names and converts them into IP addresses (name-to-IP-address mapping). You are
not required to use a domain name server unless your network connects to the
Internet. In that case you must use a domain name server.
Host Tables
If your system is on a small, isolated network, it is possible to map host names to IP
addresses using a host table. A host table is a file of host names and addresses that is
read directly in your system console.
NIS Domain Names
The Network Information Service (NIS), formerly known as Yellow Pages, is a
distributed name service developed by Sun Microsystems. NIS domains serve the
same purpose as DNS domains. Unlike DNS, however, NIS cannot be implemented at
the Internet level.
Subnet Addressing
In the DNS model, each network can be divided into a number of subnetworks (or
subnets). Within a given network, each subnet is treated as a separate network.
Outside that network, the subnets appear to be part of a single network.
Subnet addressing (or subnetwork addressing) is an extension of the IP addressing
scheme that allows a site to use a single IP address for multiple physical networks.
Outside a site that uses subnet addressing, routing continues as usual by dividing the
IP address into a network address and a local address. Inside a site that uses subnet
addressing, the local address portion of the IP address is further divided into a subnet
address (identifying a particular subnet) and a host number (identifying the host system
within the subnet).
All hosts on the same physical LAN cable are assigned the same subnet address.
Hosts on different LANs are distinguished by unique subnet addresses. All hosts on a
particular network, although possibly on a different subnet, share the same network
address.
Subnet Masks
A 32-bit subnet mask is used to identify the part of an IP address that represents the
subnet address. All bits of the subnet mask corresponding to the network address and
the subnet address are set to 1, and all bits corresponding to the host number are set
to 0.
This figure shows a Class A IP address in which the first 5 bits of the local address are
designated as the subnet address, leaving the last 19 bits of the local address to