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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
HP e3000 systems configured as gateways.
Gateways
One method of joining networks in an internetwork is by using gateways. An HP
e3000 system can have up to 256 gateways (combined number of full gateways and
gateway halves).
Full Gateways versus Gateway Halves
NS 3000/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 as follows.
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 this manual.
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 "Gateway
Configuration Scenarios".
Example 1: The node you are configuring may be a
non-gateway, such as node D in Figure
2-3 "Gateway Configuration Scenarios". 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
"Gateway Configuration Scenarios". 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."
Example 3: The node you are configuring may be a full
gateway, such as nodes B and C in
Figure 2-3 "Gateway Configuration
Scenarios". 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 "Gateway Configuration
Scenarios". 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 this manual.
In Figure 2-3 "Gateway Configuration
Scenarios", 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. If you were to
configure node E in the figure, you would enter the IP address of node F.
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, depending on the network type) and then
follow the instructions 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 "Planning for Node Configuration".
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