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Configuration 2: R7r (+CMS) <—ethernet—> R7csi 3 C-LAN Administration
Administration for Network Connectivity
CID: 77730 555-233-504 — Issue 1 — April 2000
78
> Submit the screen
End
Subnet Mask Enter the subnet mask associated with the IP address for this IP
interface.
The IP address for node-1, specified on the Node Names screen,
is 192.168.1.124. The 192 in the first octet puts this address in
the range of “Class C” addresses, which means the first 3 octets
are used for the network ID and the fourth octet is used for host
IDs.
The subnet mask defines the network and host parts of the IP
addresses. In the Subnet Mask for this example (192.168.1.224),
the 224 in the fourth octet indicates that 3 high-order bits from
the fourth octet are used to define subnets on the network
192.168.1 (224 = 128+64+32 = 11100000). The first 3 bits are
used for subnet IDs and the last 5 bits are used for host IDs.
Eight subnets can be defined with 3 bits and each subnet can
have a maximum of 32 hosts, defined with the remaining 5 bits.
Of these, only 6 subnets with 30 hosts each are usable.
The usable IP addresses in the 6 subnets have the following
ranges of values for the fourth octet: 33–62, 65–94, 97–126,
129–158, 161–190, and 193–222. The IP address for this
(node-1) IP interface, 192.168.1.124, is on the third subnet
because 124 lies in the range 97–126. Note that node 2 (adjunct,
192.168.1.125) and node 3 (router, 192.168.1.97) are both also
on the third subnet. Node 4 (192.168.1.51) and node 5
(192.168.1.39) are both on the first subnet.
The first and last IP addresses in each subnet are not usable as
host addresses because they have all 0’s or all 1’s for host IDs.
For example, in the third subnet, the fourth octet of the first IP
address is 96 (= 01100000
) and the fourth octet of the last IP
address is 127 (= 01111111
).
The “network address” of a subnet is the first IP address (the all
0’s host ID) of that subnet. In this example, the subnet addresses
of the six subnets are — 1st: 192.168.1.32 2nd: 192.168.1.64
3rd: 192.168.1.96 4th: 192.168.1.128 5th: 192.168.1.160
6th: 192.168.1.192.
See Chapter 1 for more information on IP addresses and
subnetting.
Gateway Addr Enter the address of a network node that will serve as the default
gateway for the IP interface.
Net Rgn Enter the region number for this IP interface.
Field Conditions/Comments
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