IP Addressing

[joytaylor]

Not sure if this post should go here...

We are running out of IP addresses in some parts of our network. This network 10.10.1.0 is currently using /25. I want to change it to /24. Does anyone know if I change the router's subnet mask and not change the workstation, will the workstation be able to communicate with other networks.

The problem is I don't have the resources to change the subnet mask on all the workstations at the same time. I hoping to accomplish the change in the 2 or 3 days time.

Thank you....

[m.stricker]

The workstations will be able to send traffic to the router. The issue will be what the router does with traffic. With the current subnet mask of 25, the 10.10.1.0 has 2 networks: the numbers in the range 0f 10.10.1.1-10.10.1.127 is one network and the range 10.10.1.129-10.10.1.254 is another. These are identified as the 10.10.1.0 network and the 10.10.1.128 network. By changing the mask to /24, you are telling the router to send all packets that start with 10.10.1.0 to one network.

Presumably you had a physical network using the 10.10.1.128 network address(otherwise why use a 25 bit mask?), so network traffic to it would be misrouted after the change.

[d-olds]

It sounds like you want to expand a subnet and you have 10.10.1.128/25 unused? if yes then you could add a second ip address to the router interface to that subnet.

ip add 10.10.1.0/25

ip add 10.10.1.128/25 secondary

This would allow expansion but require hosts on the same vlan to be routed to each other.