Best practice to change subnet on a live home network

[meazz1]

I upgraded mine Opnsense box to 20.1.
My home network setup as 192.168.3.0/24, the
router 192.168.3.1
At&t modem in passthru mode
IP range 192.168.3.10 -100
SSH enabled
Monitor and KB plugged into the Opnsense pc.

I want to switch my subnet to 192.168.4.0/24. What is the best way to accomplish this?

[bartjsmit]

This is what I would do:

- Start with a survey of your network so that you don't forget any clients. Fing is a handy tool (other survey apps are available).
- Set your OPNsense LAN interface to 192.168.4.1/21 to allow clients in both subnets to route to the internet.
- Test cutting over a static IP client from 192.168.3.x to 192.168.4.x and confirm that you can ping out. Set its DNS to an internet server (e.g. 1.1.1.1, 9.9.9.9, or whichever you prefer).
- Do the same for all static IP clients, testing as you go.
- When all is well, set your DHCP to issue addresses in the 192.168.4.0/24 range with a short TTL and internet DNS.
- When all clients are on the new subnet, reduce the mask on OPNsense back to /24
- Restore your old DNS server on the .4 subnet and cut over the static IP clients to it.
- Point your DHCP server to the new DNS server IP
- Set your TTL back to the old value

Test often and good luck!

Bart...

[michael]

This is what I would do:

- Start with a survey of your network so that you don't forget any clients. Fing is a handy tool (other survey apps are available).

I just look up the network devices via OPNsense reporting of all the LAN DHCP leases at:
https://192.168.1.1/status_dhcp_leases.php
Am I missing something?  Or is it better to use another tool?

[bartjsmit]

I just look up the network devices via OPNsense reporting of all the LAN DHCP leases at:
https://192.168.1.1/status_dhcp_leases.php
Am I missing something?  Or is it better to use another tool?

That's a good start, but there are a lot of devices these days even at home. If you miss a static IP, it will drop off your network after the switch. A quick sweep may save you headache later.

Bart...

[mitchel]

Thanks Bart!  I know it has been a while since you wrote that but it is just what I was looking for.