/29 subnet mask explained with an example
/29 subnet mask is created by subnetting the default network ranges.
/29 can be written as follows in binary
11111111.11111111.11111111.11111000
In numbers, /29 becomes 255.255.255.248 so where we cannot enter the CIDR notation, we have to enter the subnet mask in numbers.
29 bits out of 32 represent the network ID while only three bits represent the hosts. We have 8 IP addresses per subnet if we use this subnet mask in our network.
Out of 8 available IPs, we can assign 6 IPs to our devices in the network. This subnet mask is used in small networks where we need only a few devices.
We can create /29 subnets from any available network however in this example we will default class c network 192.168.10.1/24
We will find the network ranges that we can use while using the /29 subnet mask.
We have 3 host bits so we will multiply 2x2x2 to find out the increment. 8 is our increment, now we can add 8 IPs in each subnet.
192.168.10.1 – 192.168.10.7
192.168.10.8 – 192.168.10.15
192.168.10.16 – 192.168.10.23
192.168.10.24 – 192.168.10.31
192.168.10.32 – 192.168.10.39
192.168.10.40 – 192.168.10.47
We can continue to create IP ranges according to our requirements; we can create up to 32 smaller networks from one default class c subnet.
The below exercise needs a good understanding of VLAN and subnetting so you can check the VLAN tutorial and subnetting practice questions before working on the exercise.
The following example network is created using 255.255.255.248 subnet mask, find out the missing IP addresses, and correct the wrong IP addressing.
Answers
- The IP address assigned to the router is the network ID that cannot be assigned to the device; we can assign any IP address from 192.168.10.2 to 192.168.10.6 range.
- The default gateway of the PC has been assigned the IP address from the 192.168.10.1 network so we can assign any IP from this range to the PC.
- This PC can be assigned the IP address from the 192.168.10.1 network.
- The IP address assigned to the interface of the router is correct.
- The IP address assigned to the router’s interface is the broadcast ID so we have to correct the configuration and we can assign an IP address from the 192.168.10.9 to the 192.168.1.14 range.
- The IP address assigned is correct.
- The IP address assigned to the PC is from the 192.168.10.8 subnet however this PC is part of VLAN 10, one VLAN represents one network so we have to assign the IP address from the same network that is configured for VLAN 10. We can assign IP from 192.168.10.2 to 192.168.10.6 range.
- The IP address assigned to the PC is correct.
