[Solved] Router DHCP settings


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Edit See post below - TL-DR - it's about accessing your home network via a public router which is very likely to have the same subnet as you home network unless you change it to something a bit unusual, hence Ed's 10.10.20.x or something similar. I remember back in the 90's I had a modem router that came with a 10.0.0.1 default gateway IP so my PC would be 10.0.0.2 - life was simpler back then ;)

 

I'm very new to unRAID - I started a server last year and then had to tear it down to build a home learning PC for my children. Last year I watched a ton of SpaceInvader One videos but honestly what I've retained and properly understood is going to be patchy at best. Somewhere in the murky depths I've got a niggling memory that I should alter the default DHCP settings on my router (running asuswrt-merlin) so as to avoid a future potential conflict. Now I can't remember where I got that snippet from, or what it was about? Maybe something to do with pfsense set up in a VM? Maybe NGINX or Pi-Hole or any one of a dozen different projects I've watched videos about and I'm excited to explore in future . . .

 

I faintly recall that the issue was something to do with security or avoiding a clash between the home network and setting up WAN access to my LAN, and something to do with why the default 192.168.1.1 or 192.168.0.1 to 192.168.x.255 should ideally be changed to something else, such as 10.10.1.1  ?

 

As such a change would be temporarily pretty disruptive to my family's internet access I obviously need to understand why I'd do it, what the benefit is and what future projects this is tied into?

 

So far I've wasted several hours attempting to rewatch previous videos and drawn a blank. I've only hit upon the understanding that I should reserve some DHCP addresses to be manually assigned to PC's and devices on my home network (obviously including making the unRAID server IP static) and so change the pool of available addresses to be randomly assigned - but that doesn't explain why I'd need to change the address numbers I'm using from the defaults?

 

If anyone can answer or just speculate about why and when this is useful I'd much appreciate it. Thanks for reading this far!

Edited by awediohead
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The usual reason for setting static IP addresses on the router instead of on each device is that by default every device is already set to DHCP, and all of the management can then be handled in one place.

 

The other is that assuming that at some point you change your router.  The replacement hands out addresses of 192.168.1.x and the original handed out 192.168.0.x   Any device that you had set on the device itself with a static IP would now be unable to communicate when connected to the replacement router.  By doing the management on the router itself, all devices would still work (albeit not on the IP address you want), and you can simply adjust the settings there, rather than on the device which may be a pain to get at if you can't access it due to the wrong subnet.

 

Beyond all that, I'm a fan of always having static IPs for every device that's permanently connected (ie: ethernet) and only utilizing DHCP for mobile devices.  

 

Changing the pool of available addresses for DHCP is so that any static addresses you may set do not possibly conflict with an address being handed out via DHCP.  But, truth be told I've never seen a router that ever hands out a conflicting address, and if I did I'd probably immediately replace the router as it is too completely brain-dead for me to trust it to do anything right at all.

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Thanks for the reply - that's what I'd understood.

 

My problem is that there was a specific reason why it was recommended to change the default (in my case 192.168.1.x) address range to something totally different -

 

On the Space Invader PFsense videos (hosted in unRAID VM and hardware) he uses 10.20.10.x for one LAN and 192.168.2.x for another, but I suspect that's just to avoid confusion. One LAN goes through his VPN to appear to be based in the USA, another goes through the VPN to appear to be based in Germany and a third (his games consoles) connect directly without VPN so as to be based in London. So I understand why you would choose different DHCP address ranges on separate LANs to make them immediately visually distinct. But not why you would need to change what you've already got, to something else . . .

 

Sorry I just remember watching something a few months ago that made me file away, "Right, so I have to change the address range my router's static or dynamic DHCP is selected from, BEFORE I set up my unRAID server, if at some future point I ever want to do "X". . . . .  but I cannot for the life of me remember what "X" is, just that it was something of an 'A Ha!' moment at the time and something that sounded interesting.

 

If no one here has any clue then I probably just misunderstood the whole thing!

 

 

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Sometimes you also just don't want any communication between different networks.

 

eg: I'm cheap and can't be bothered to buy a switch that supports VLANs, but I do have various routers available, and have set up things like my Ring Door Bell, and the Alexa's to all run off of a separate router so that the IoT devices (which I do not completely trust from a security standpoint) have zero access to the rest of the network.  Even some so-called "trusted devices" (ie: my wife's phone / tablet) I keep off the main network since I'm not 100% in control of them.  I don't know about you, but I seriously doubt that any manufacturer for a smart-plug is ever going to release any firmware update for them....

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Thanks that makes sense. I don't have any smart or IoT type devices - but I do have a teenager who's almost a walking, talking security vulnerability by definition!

 

I'll post back if I ever manage to remember what 'X' is or track down the reference.

Cheers

 

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17 hours ago, awediohead said:

Right, so I have to change the address range my router's static or dynamic DHCP is selected from, BEFORE I set up my unRAID server, if at some future point I ever want to do "X"

Probably referencing connecting 2 different LANS with a VPN.

https://serverfault.com/questions/548888/connecting-to-a-remote-server-through-a-vpn-when-the-local-network-subnet-addres

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  • 2 weeks later...

Ah ha! Found 'X' !

 

- explanation at 8:55 about using less common subnets on home router to avoid conflicts with using openVPN from hotels and internet cafe's which are likely to have bog standard 192.168.1.1 and therefore conflict with the home router's subnet you're trying to connect to:

 

 

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Yep for my system I use 192.168.7.x simply because its a little different

 

I set that up by assigning a Static IP to my Server and in my Router I enabled a reservation for it so it will not hand out the IP of my server to any other device. As well I have a few other devices in my house like my Nest Thermostat and my Neato robot vacuum that for some reason like to fall off the network and reconnect. When they fall off they often had issues reconnecting so I put reservations on them too so they always reconnected with the same IP which seems to fix their bizarre behavior. 

 

Oddly enough the mention of my Nest in the Paragraph above even with my Server set with a Static IP and reserved in my router my Nest some how obtained the same IP as my Server and when I watched a video file off my server I discovered I couldn't connect or control my Nest Thermostat. Took a bit of detective work and found out that my Nest was defaulting to the same IP that I set my Server too when it lost connection. Lol Made no sense to me either, but not any more. 

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  • awediohead changed the title to [Solved] Router DHCP settings

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