@NetworkAdmin 

Does not appear to be able to change to that.

You could opt for 172.16.4.1 or 10.0.4.1.

I am assuming it has to do with the Deco looking at the 192.168.x.x and taking it as only a class C IP subnet so putting in 255.255.252.0 confuses it.

@NetworkAdmin I realise this is an older post, but I have the same issue as stated above and the reply to that last post is unclear to me.  Here'e my situation:

My Deco, when it resets (say from a power outage), will change it's IP to it's seeming default of 192.168.0.1 even when I've set it to previously 192.168.1.1.  This requires me to go into the app and fix the IP back to 192.168.1.1 each time, so since we've had several outages and resets, I decided just to let the Deco go to it's default of 192.168.0.1 and just change my subnet mask to 255.255.252.0 so I don't need to fix the IP any time there's a reset.

However, when I try to set the subnet mask to 252 with the IP 192.168.0.1, I get the "failed" message in the app.  It will not allow the 255.255.252.0 subnet mask to be applied when my Deco IP is 192.168.0.1.

I am unable to get the IP 192.168.1.1 to "stick" on the router, so any time I lose power the IP reverts to 192.168.0.1 and I lose connection with devices on my network which have statically assigned IPs until I change the Deco IP back to 192.168.1.1.  Was the response above telling me that I am unable to use the 252 subnet mask specifically with the IP 192.168.0.1, and that I CAN use that subnet if I select another IP for the Deco?  If so I'm still in a pickle because I'll need to change all the static IPs on my network to reflect that new subnet.  

The other solution would be to make the router stop defaulting back to 192.168.0.1 if it resets.  Is there some way of which I am unaware that I can stop it from doing that?

Thanks!

@StayAtHomeBob,

I spent alot of hours trying to make sense of TP-Link's implemenation of LAN definitions for this device and could not figure out why their application is not permitting certain "custom" netmasks for the 192.168.0.0/16 space.  At first I figured it had to do with classful networks and wondered if it was a class C limitation, but in a private class c the IANA clearly states that its common practice to subdivide ranges into smaller subnets.  I quickly gave up on trying to make sense of the design.

Like you, I had many static IP addresses and am also a fan of DHCP Reservation (aka static DHCP).  When I upgraded to the deco, I tried very hard to bring my 192.168.4.1/22 subnet with me, but was not able to as described in the first post.  In the end, I had to setup the DECO  LAN subnet to 10.0.4.1/22. (LAN IP = 10.0.4.1, Subnet Mask 255.255.252.0).  Of course, this meant I had to change all my static IPs by hand and  yes it was painful.

The configuration, however, is persistent across power outages and reboots so I'm not sure why yours is resetting.  I have a huge list of DHCP reservations defined and have never lost them, but I keep a print out of the info just in case I do.  I've created another thread on this forum to TP-LINK where lots of others users have jumped onboard to push for the ability to backup router configurations and be able to restore them in the event of a factory reset.

Since writing this thread and others, there have been no firmware updates and the TP-Link moderators just keep saying "we'll share with our development team"  but nothing happens.  At this point, my best guess is that the subnet issue is a mobile app software limitation and nothing more.  From a pure networking perspective I see no reason why what you're trying to do shouldn't work.  There does not appear to be any internal conflict but having such a locked down interface its hard to say for sure.  I tried many different areas of the 192.168.0.0/16 network with the same results.

Sorry I dont have a better answer for you, but I encourage you to push TP-Link for a fix or at least a meaningful response.

@NetworkAdmin 

I made another inquiry about this and was told that yes that the subnet can not be modified to what you want it, but that was not going to stay that way. Apparently, there will be a future update that will change this.

@Tony Thanks, I appreciate your followup.  I'll look forward to updates as they come out.

Is resetting the LAN IP address when there is a power failure (or perhaps an Internet glitch) a common problem with TP-Link routers?

I've had issues with a TL-WDR3500 ever since I started using it where it changes back to the default LAN IP address every day or two & sometimes cannot be changed to what works because I get Error Code 5008.

@NetworkAdmin Hi, The same is happening to me. I have default LAN IP: 192.168.1.1 and when it resets goes to 172....

The real issue is when I try to come back to my previous IP, I can not put the 192.168.1.1. Sometimes I have to try several times an rebot the routers. It is really annoying and generates a lot of issues in my CCTV system

The problem I had was changing the LAN IP address to 192.168.1.1 and getting it stay so that it did not conflict with the modem’s IP address.

What frequently happened was the router’s LAN IP address reverted back to its default 192.168.0.1 for some unknown reason. And changing it back to 192.168.1.1 was usually difficult to do & I would get an error message. What I noticed is that the router’s WAN Subnet Mask had changed to 255.255.0.0. for some unknown reason, and this prevented me from changing the LAN IP address. I need the WAN Subnet Mask to be at its default 255.255.255.0 but there was no way to change it, at least not that I found.

Sometimes playing with the WAN connection type would reset the IP to 255.255.255.0, but the last time it did not work. I took the router out of the system but left it powered on. When I came back about a day later to work on it the WAN Subnet Mask had reset to the default 255.255.255.0 that I needed. I have no idea what triggers it to change or if there is a way to manually do it, other than perhaps doing a router reset.

Some comments I've read say a router suppose to reset to default settings if it experiences a conflict. And maybe that's what happens to mine. But if it's part of a home security system how are you supposed to access the router if you're away on vacation?

Got the issue too when I tried to replace the Lan IP from 192.168.2.1 to 192.168.2.2 on my Deco M4 main router to prevent a conflict with my ISP router. I got the "Failed to..." each time. But then the connection become unstable. I then power cycled the main router to see that the saved new Lan IP was now active. It looks like changing the Lan IP was simply killing the connection but the application wasn't able to handle it. It should have started a router restart and a wait message.

Everything goes fine now!

@Tony, Any updates on when this will be implemented?