For this example, we'll setup a Class C network with no subnetting.
Our Legal addresses will be the entire class C domain which is 203.191.158.xxx where xxx can vary from 0 to 255.
I will illustrate the addresses by showing the decimal address to the left and then showing the binary representation of the address to the right.
Router IP :203.191.158.___ 11001011.10111111.10011110.________
We are going to assign the Router a node number of 10 so the full address becomes:
Router IP :203.191.158.10 11001011.10111111.10011110.00001010
The subnet mask is the next step and since there is not subnetting we'll use the standard Class C subnet Mask which is:
Subnet Mask :255.255.255. 0 11111111.11111111.11111111.00000000
<--net-| |-node-->
A more detailed explaination of what the Subnet Mask does is define where the dividing line between the network (or quite literally the cable ID) and the node (or the ID of an individual device on the cable.)
The broadcast address bears a heavy relation to the subnet mask. An operational definition of the broadcast address is that the network portion of the broadcast address is identical to what we have assigned the router and the node portion of the address is set to either all 1's (the ones broadcast) or all 0's (the zeros broadcast.) Both are legal but whichever one is chosen must be used consistently on the network.
As defined by the subnet mask above, the two legal broadcast addresses can be either:
Broadcast(0's):203.191.158.0 11001011.10111111.10011110.00000000
<--net-| |-node-->Broadcast(1's):203.191.158.255 11001011.10111111.10011110.11111111
<--net-| |-node-->
For our discussion we will use a ones broadcast address so our Broadcast address will be:
Broadcast :203.191.158.255 11001011.10111111.10011110.11111111
<--net-| |-node-->
If there is a router on our network that let's us reach The Internet or other resource. The address of this router is added to the field Default Router, else we'll leave it as zeros.
If there is a Domain Name Server (DNS) on our network or there is one provided by the Internet Service provider, the field Name Server will get the address of the DNS, else we'll leave it as zeros.
In this example this is a Class C network with subnetting.
From our sys-admin, we are told:
203.191.158.65
255.255.255.192
The sys-admin did not tell us everything but there is enough information complete our task.
That subnet mask tells us that our network has been divided into different pieces, all (hopefully) joined by a backbone router.
The subnet mask is the next step and since it will tell us what are valid addresses are.
Subnet Mask :255.255.255.192 11111111.11111111.11111111.11000000
<--net-||-node-->
This tells us that the Class C network has been divided into four separate network segments and (focusing on the last octet only) the ranges of each of the subnets are:
Zeros Broadcast| |Ones Broadcast Dec Binary Dec Binary .0 .00000000 to .63 .00111111 .64 .01000000 to .127 .01111111 .128 .10000000 to .191 .10111111 .192 .01000000 to .255 .11111111
The address of the backbone router falls in the second group so the legal range of our IP addresses are from .64 to .127
A more detailed explaination of what the Subnet Mask does is define where the dividing line between the network (or quite literally the cable ID) and the node (or the ID of an individual device on the cable.)
The broadcast address bears a heavy relation to the subnet mask. An operational definition of the broadcast address is that the network portion of the broadcast address is identical to what we have assigned the router and the node portion of the address is set to either all 1's (the ones broadcast) or all 0's (the zeros broadcast.) Both are legal but whichever one is chosen must be used consistently on the network.
As defined by the subnet mask above, the two legal broadcast addresses can be either:
Broadcast(0's):203.191.158.64 11001011.10111111.10011110.01000000
<--net-||-node-->Broadcast(1's):203.191.158.127 11001011.10111111.10011110.01111111
<--net-||-node-->
Since we were instructed to use a ones broadcast, our Boradcast Address will be:
Broadcast(1's):203.191.158.127 11001011.10111111.10011110.01111111
<--net-||-node-->
Since there is a backbone router on the network, the address of this router 203.191.158.65 is added to the field Default Router.
If there is a Domain Name Server (DNS) on our network or there is one provided by the Internet Service provider, the field Name Server will get the address of the DNS, else we'll leave it as zeros.