/26 subnet mask

/26 subnet mask with practical examples

/26 subnet mask in binary is 11111111.11111111.11111111.11000000 so the subnet mask becomes 255.255.255.192

This is the subnetted network in which two host bits in the last octet is converted to network bit.

128 64 32 16 8 4 2 0

1     1    0  0  0 0 0 0

192 in the last octet has been obtained by adding 128+64

/26 subnet mask creates 4 subnets if we have a default subnet mask of /24. In case of network administrator wants more networks however host requirement is less per network then using /26 as a subnet mask will provide 4 networks with each subnet having 64 IP addresses.

From the available 64 IP addresses, 62 can be assigned to the devices available in the network while the other two will represent subnet ID and broadcast address.

/26 subnet mask Example

We have an IP address range that can be assigned to the internal LAN of our company.

199.200.5.0/24

According to the new requirement in the organization, 4 internal networks are required. Each network will have a maximum of 50 devices.

To fill the above requirements, a network admin can use the /26 subnet mask to create the required networks.

New IP address ranges will be as below

199.200.5.0     – 199.200.5.63

199.200.5.64   – 199.200.5.127

199.200.5.128 – 199.200.5.191

199.200.5.192 – 199.200.5.255

/26 subnet mask exercise

Assign the appropriate IPs to the devices in the network and correct the IP address configuration.

Answer

1. PC2 can be assigned the IP address from the subnet 199.200.5.0/26 because the router interface has been assigned the IP address from this subnet and PC2 should be part of VLAN 5 as only one IP address has been assigned to the router’s interface.
2. Three networks are already in use in the network diagram except subnet 199.200.5.192/26 so we can assign the host IP from this subnet to the router’s interface.
3. PC0 is part of network 199.200.5.128/26 so we can assign any IP address from the range 199.200.5.129 to 199.200.5.10.
4. The IP address that has been assigned to the router’s interface is the network ID so we have to assign the valid host IP address to correct the configuration.
5. PC5 is part of VLAN 5 so this PC should be on the 199.200.5.0/26 network as one VLAN represent one network. Although the IP address assigned is from the correct network, however, this IP address is the broadcast address so we have to use the valid host IP.
6. PC1 is from VLAN 5 however IP address assigned to PC is from a different subnet that does not represent VLAN 5 subnet so we should use the IP from subnet 199.200.5.0/26.
7. PC3 can be assigned to the IP address from 199.200.5.192/26 subnet. As the switch connected to the router has two different VLANs, we should create a sub-interface on the router’s interface that is connected to the switch and assign two IP addresses so the router can handle the traffic from two different networks.