Using The Node As An Ip Gateway; Required Configuration; Subnet Addressing - Cabletron Systems Netlink FRX4000 User Manual

Subnet Addressing

Using the Node as an IP Gateway

Required Configuration

Configuring IP
Multiple physical networks can use a single IP network address. This is done by using
a portion of the node identifier (it does not need to be in complete octets) as a "subnet"
identifier. For example, in a Class B network, the first and second octets are the
network identifier, and the third and fourth are the node identifier. If the network con-
tains the maximum of 65,025 nodes, management will most likely be easier if the third
octet of the IP address is used to define up to 255 subnets on the network. The fourth
octet can then define up to 255 nodes on each subnet, effectively providing unique
identifiers for all 65,025 nodes on the network.
As described earlier, the first octet of the IP address identifies the network's class:
= A, = B, and
0–127 128–191
it knows how many octets are supposed to identify the network and how many are sup-
posed to identify the node. When part of the node identifier is used as a subnet iden-
tifier, there must be a method of telling IP of the modification. This is done with a
subnet mask. The mask is created by taking the 32-bit (binary) IP address, then sub-
stituting a for every bit that identifies the network or a subnet, and a
1
that identifies a node. When IP applies this mask to an actual IP address, it can see
which bits identify the subnet and which identify the node. (IP already knows the
network's class, and therefore which bits identify the network.)
An FRX4000/6000 can function as an IP gateway, and forward IP packets. This
requires that IP be configured (and loaded) in the
To run IP in an FRX4000/6000, you must first configure the following in the database:
Node parameters, which is general configuration that must be done no matter
which protocols will be run in the node. See Chapter 4.
RLPs that will contain the interface(s) to the user device(s), plus Line Interface
Card(s) supporting the ports that will be the interfaces. See Chapter 5.
Protocol(s): IP, RIP, and frame relay or X.25. See Chapter 5.
LAN interface(s)
Frame relay port(s)
relay PVC. See Chapter 7 (frame relay) or Chapter 8 (X.25).
IP parameters described in this chapter.
= C. Once the Internet Protocol knows the class,
192–223
that will connect to any attached LAN(s). See Chapter 5.
and/or X.25 port(s) that will connect to a network or frame
for every bit
0
RLP file (described in Chapter 5).
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