Renumbering my network. Any pitfalls?

LeiShen

I should also mention I have a 4 port Router currently set up as:

Port 1: 192.168.1.x
Port 2: 192.168.2.x
Port 3: 192.168.3.x
Port 3: Wan to Modem

So I want to keep these subnet separate, so maybe moving to a Class B Address is not a good idea?

Or for a Class B, like 172.16-31.x.x, perhaps set it like this?

Port 1: 172.16.x.x
Port 2: 172.17.x.x
Port 3: 172.18.x.x
Port 4: Wan to Modem

I guess I could stick with 192.168 and just reassign like this, maybe it would be uncommon enough:

Port 1: 192.168.201.x
Port 2: 192.168.202.x
Port 3: 192.168.203.x
Port 4: Wan to Modem

Thoughts, opinions, pitfalls?

Thanks!!

KOM

There is nothing magical about IP addresses. Just pick a subnet and renumber. Use anything in the rfc1918 space you want:

10.0.0.0/8
172.16.0.0/12
192.168.0.0/16

They are completely interchangeable. There is nothing spooky about 172.16.0.0/12, just people aren't as used to seeing it as they are with 192.168.0.0/16.

LeiShen

So I could something like:

Port 1: 172.17.1.x
Port 2: 172.17.2.x
Port 3: 172.17.3.x
Port 4: Wan to Modem

With a netmask of 255.255.255.0 and that wouldn't break anything?

Thanks!

NogBadTheBad

This post is deleted!

KOM

I have no knowledge of your network configuration so I can't say it wouldn't break anything, but there is always going to be disruption if you renumber a network.

TheNarc

The opportunities for things to "break" should really only arise in places where you're counting on certain devices being assigned specific IPs. For example, if you have any DHCP static mappings configured, aliases, port forwarding rules, etc. you'll need to review and update them as necessary. But the devices on your network themselves don't care what IPs they get.

Derelict

$ randomlan
10.138.112.0
172.18.173.0
192.168.111.0
fdb4:b660:d594::/48

LeiShen

Well, that was a little painful. But its done!
Used the 172.17.x.x private block.

LAN1: 172.17.1.x
LAN2: 172.17.2.x
LAN3: 172.17.3.x

With net masks of 255.255.255.0

I also configued DHCP Server and DNS Resolver for as many of the 'static' devices as I could on the network so I won't have to poke at each one if I every do this again. Also set up DNS Resolver for those DHCP devices so I can find them all by name now - I know, its pretty basic, but 'new to me'!
The only real gotcha was the Wifi Routers: Gotta log into a different interface than the one your working on, otherwise poof you're no longer connected! :)
Plus they are all in Bridge mode, and with LinkSys routers, if you put them in DHCP mode and Bridge Mode, they disappear from the network and you can no longer access their Admin pages: caveat emptor!
So they had to be kept Static IPs.
Thanks for everyones' help and reassurance! No more cross-network conflicts!!
Yay!!!

Derelict

@leishen said in Renumbering my network. Any pitfalls?:

No more cross-network conflicts!!

Until there are. IPv6 will make this a virtual impossibility.

But 172.17 should pretty much eliminate them for you for now. Good move.

Derelict

Let this thread serve as an example of seeing the problem, setting a maintenance window, and renumbering. It can be a MUCH better path than trying to NAT all the things because you decided to deploy 192.168.1.0/24 or, much worse, 10.0.0.0/8.