HP 3000 Manuals HP 3000 Manuals
Internetworks
Two or more networks of the same type or of different types can be linked
together to form an internetwork or internet. For example, if you wanted
to connect the nodes in a point-to-point network with the nodes on a LAN,
the combination of the two networks would be called an internetwork.
Creation of an internetwork allows any node on one network to communicate
with any node on another network that is part of the same internetwork.
Up to 256 individual networks can belong to the same NS internetwork.
The divisions between the networks in an internetwork are called network
boundaries. Nodes in each network will have the same network address
(network portion of the IP address); however, each network within the
internetwork will have its own unique network address.
The networks in an internetwork may be connected by a bridge or router,
or by 900 Series HP 3000 systems configured as gateways.
Gateways
One method of joining networks in an internetwork is by using gateways.
An HP 3000 system can have up to 14 gateways (combined number of full
gateways and gateway halves).
Full Gateways versus Gateway Halves.
NS3000/iX allows you to choose between connecting two networks with a
full gateway or connecting them with two gateway halves. A full gateway
is a node configured as a full member of two (or more) networks for the
purpose of passing information between the networks to which it belongs.
The node is considered a member of each of the networks for which it is
configured.
A node that is a gateway half is configured as a member of a network and
as a partner of another gateway half. A gateway half link that joins two
networks connects two nodes (a gateway half pair) by a point-to-point
link (NS Point-to-Point 3000/iX Network link). The gateway half link and
pair is not considered a network itself. Each of the paired gateway
halves is configured as a member of a different network (the two networks
to be connected) and as a gateway half on the same gateway half link.
Together, the two gateway halves function as a full gateway.
Gateway Configuration Overview
Gateway configuration includes both identifying neighbor gateways in each
node's configuration file and configuring gateway half NIs for nodes that
will serve as one half of a gateway half pair. These tasks are described
below.
Identifying Neighbor Gateways.
If you are including gateways in your internet configuration, you may
want to modify each node's configuration file so that the node is aware
of all of its neighbor gateways
(gateways on the same link). You accomplish this during configuration of
each network interface for which you want to allow communications over
the gateway. You will find step-by-step instructions for identifying
neighbor gateways in each of the link configuration sections of this
manual.
An alternative to identifying neighbor gateways in every node's
configuration file is to configure a default gateway for the node.
Instructions for doing so are included in chapters 5 and 6.
The next pages show several examples of gateway configuration.
Neighbor Gateway Examples.
When using NMMGR to configure any node, you will be entering the
identities of all the neighbor gateways into the configuration of the
node. The following examples illustrate several gateway configuration
scenarios based on the network represented in figure 2-3.
* Example 1: The node you are configuring may be a non-gateway,
such as node D in figure 2-3. You would need to enter the
identities of each of its neighbor gateways, in this case nodes C
and E, at the Neighbor Gateways screen. On the Neighbor Gateway
Reachable Networks screen, you would also enter the IP addresses
of networks 1 and 3 as two of the configured reachable networks
reachable through gateway Node C.
* Example 2: The node you are configuring may be a gateway half,
such as node E in figure 2-3. You will still need to enter the
identities of the node's neighbor gateways as you configure the NI
(in this case, node C is the neighbor gateway). You will also
need to configure a gateway half NI for the node, as described
under "Configuring a Gateway-Half Pair" below.
* Example 3: The node you are configuring may be a full gateway,
such as nodes B and C in figure 2-3. Though full gateways are
never actually identified as such in the configuration process,
they too, must know about the other gateways. If you were
configuring node C, you would identify nodes B and E and neighbor
gateways.
* Example 4: One of the gateways on your internetwork may be
designated as a default gateway, such as node C in figure 2-3.A
default gateway is a gateway that is designated to receive any
traffic for which the network is unable to identify a destination.
You must identify the node as a default gateway in the
configuration file of each node that will access it as the default
gateway. If you were configuring node D, you would identify node
C as a default gateway by entering an at sign (@) in one of the IP
address fields of the Neighbor Gateway Reachable Networks screen.
Only one gateway may be designated as a default gateway for each
node. The default gateway must be on a LAN or token ring network.
Configuring a Gateway Half Pair
If you are configuring a gateway half pair, you will need to configure a
gateway half NI for each half of the gateway pair. You will find
step-by-step instructions for configuring a gateway half NI in chapter 9
of this manual.
In figure 2-3, nodes E and F form a gateway half pair. When you
configure a node as a gateway half, you enter its partner's IP address
into this gateway half's configuration in the Gatehalf Configuration
screen. I you were to configure node E in the figure, you would enter
the IP address of node F.
![[]](../../pic3k/M013399/FFN43c50.gif)
Figure 2-3. Gateway Configuration Scenarios
Gateway halves require the configuration of two separate network
interfaces on each node: one for the gateway half, the other for the
network it interfaces to (for example, a LAN or point-to-point NI). You
will need to follow the instructions for the specific NI type (see
chapter 5, 6, 7, or 8, depending on the network type) and then follow the
instructions in chapter 9 to enter configuration items specific to the
gateway half NI.
Worksheets that will aid you in planning for internetwork communication
are located in chapter 4.