TCP/IP Configuration and Management Manual

NonStop Systems Used as Internet Gateways
TCP/IP Configuration and Management Manual—427132-004
F-9
Startup Files for HOST1
The address 127.1 or 127.0.0.1 is the standard for loopback operation.
ROUTE Objects
A ROUTE object is added for each remote subnet destination with which this host will
need to communicate. The Route object specifies the destination network IP address
and the gateway IP address to which this host is physically connected.
GATEWAY Attribute
In this sample TCP/IP environment, there are potentially three destination networks to
which HOST1 could communicate and thus, three routes, one for each destination
network. Notice that in this case, the gateway address is the same for each route. As
Figure F-6
shows, HOST1 must route a datagram destined for one of those three
networks through GTWY1, which has the IP address of 150.50.192.1. This method is
especially useful when you have multiple gateways to multiple networks. When all the
routing is through a single gateway, however, there is a simpler way to set up your
routing.
Default routing establishes a single route as the default route. This action is particularly
useful when you know that most of your TCP/IP traffic is going through a single
gateway, as in the case shown in Example F-2
. The single route added for the second
NonStop TCP/IP process ($ZTC1) in Figure F-6
implements default routing. What
indicates that this is a default route is the use of 0.0.0.0 to designate the destination
network IP address. You can add more routes for those networks which cannot be
reached by using the default route.
Subnet Mask
The subnet mask is not altered in this file. The default mask of %hFFFF0000 is
adequate. Because this sample configuration uses a class B IP address on a network
without subnets, the first two octets of the IP address are adequate for determining the
proper network.
Be aware that adding subnets and routes is not the same as implementing subnetting.
This sample configuration configures a host (HOST1) connected to a single network,
which is connected to another network through a gateway (GTWY1). Neither of these
two networks has implemented subnetting. (For subnettting information. see
Configuration 2: Startup Files for a Host in a Subnet Addressing Environment
on
page 3-8 and Subnet Addresses
on page B-5). The use of the SUBNET object simply
means implementing TCP/IP within the NonStop environment.
Then, all the subnets and routes of the NonStop TCP/IP processes $ZTC0 and $ZTC1
are started.
The HOSTS File
The HOSTS file is the file used in the absence of a Domain Name Server for resolving
the common names of hosts into their corresponding IP addresses. (The HOSTS file in
Example F-3
is customized for the purpose of this sample environment.)