Dahua Cams - Change Subnet - No longer work with NVR

Hi Everyone,

Been pulling my hair out for 24 hours.

I have a Qsee Qt8516 with the most current firmware. I have 16 Qsee/Dahua 2-4mp cameras. The system has been functioning well for over a year.

Yesterday I had to increase the ip addresses in the house.

Our previous IP's were 10.10.1.xx on a subnet of 255.255.255.0

I have never expanded a subnet range, so perhaps I did something wrong. But I changed the subnet to 255.255.252.0

I Changed the NVR and the Cameras static IP's to 10.10.3.xx

13 of the 16 cameras attach without any issue.

But I have 3 that refuse to work. From the Qsee NVR - it locates the 3 cameras and you can add them - but they never connect. From the QTview software you can 'find' the camera but an image never appears.

From a browser you can directly connect to all 3 problem cameras without any issue.

From the Qsee IP tool - it does not see the 3 problem cameras.

I downloaded the Dahua IP tool - and it only sees the 3 problem cameras. And while it sees them and lets me view the camera image - I cannot reset the 3 trouble cameras to factory default.

This is driving me nutz. Qsee tech support spent 2.5 hours on teamviewer and then just vanished without saying goodbye.

Any idea -- I must have some kind of a subnet setting set wrong but I can't imagine what since everything is pinging back and forth.

Thanks Dave B

o2manyfish said:

I have never expanded a subnet range, so perhaps I did something wrong. But I changed the subnet to 255.255.252.0

Click to expand...

this should be 255.255.255.0 normally.
to increase your ip range that is set normally in your router eg 192.168.1.1-------192.168.1.250

Are all of your cameras identical? Are they directly connected to the NVR or external POE switch? If everything is working except for 3 cameras it seems like you did everything correctly and there is just a problem with those three cams (obviously).

Marku - Setting the Router for 192.168.1.1 - 250 - Only gives you 253 ip addresses. You can't just get to 192.168.1.254 and then start counting again at 192.168.2.1. To go up to the next increment you have to change the subnet. From my reading (and this is my first time working with subnets) if you change the subnet from 255.255.255.0 to 255.255.252.0 then you can use 192.168.0.. / 192.168.1.. / 192.168.2... etc --- So now you can have up to 1000 users.

I need more that the 250 that 255.255.255.0 subnet allows. And yet I can't seperate the different devices I want to group physically onto different networks. .


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Spankdog,

I have 6 different models of cameras on the property. The 3 that are not linking are not identical to each other, nor identical to all the others that are working. There are 2 other cameras of the same model that are working and 1 is not.

The strange thing is that ALL 16 cameras hooked up and worked without issue when I had just one subnet - Now by increasing the subnet - 3 cameras don' want to play nicely.

The cameras are plugged into POE switches all over. 2 of the non working cameras have a working camera plugged in an the same switch.

And remember - these 3 cameras are 100% working and functional as stand alone cameras - But they are not working properly with the NVR or the viewing software (for camera groups) - As individual cameras - all 3 are working.

Thanks for trying to help.

Changing the subnet mask changes the size of the network and the number of hosts on the network.
255.255.255.0 is a /24 bit mask which will allow you to have 254 devices on your network.
255.255.252.0 is a /22 bit mask allowing you to have 1022 devices on the same network

For a home sized network, I cannot see any reason why you'd not use a /24 bit mask (255.255.255.0).

Subnet Mask Cheat Sheet has more info

Valiant,

Thank you for the post and for the link to the cheat sheet. The reason I upped the subnet is that I have a techie house and we were already over 200 ip devices. I'm constantly adding more and more IP switches and outlets. I've been trying to organize the types of devices into IP groups .10-.25 (Computers, servers, storage) / .50 to .80 (Telephones) / .100-.130 (Security Cams) / Av Equipment / etc - And now with Security system and home automation the addresses are just flying out.

My house, yard, garage all buildings are wired with CAT 6 and Ubiquiti Wifi - But I can't physically move the groups to different LANs.

I thought the best way to go past the 250 ip addresses was to go up to the next subnet. But I really don't understand the differences in the 22bits /14 bits, etc.

While from a mechanical aspect (to me) it seems like the devices shouldn't have any issue, I am wondering if because these are all consumer products and not commercial products if they aren't designed to operate on a subnet other than 255.255.255.0

Am I making sense?

Again, thank you for trying to help. When I clicked on the Mask Cheat Sheet - other than seeing that by going to 255.255.252.0 gets me to 1000 addresses - I don't understand any of the other things on that page....

Dave B

There is no difference in commercial/home products with subnet limitations. If you wanted to allow for more hosts, a /23 bit (255.255.254.0) subnet mask will allow 510 devices, because the extra (lost) bit is gained by the host portion (9 host bits). Good network designers however REDUCE the size of their networks, not increase them. The less devices in a 'broadcast domain' means limiting broadcast traffic (such as arp). Too many devices could impact performance and that is why VLANS are often created.

For your network, I'd be checking for duplicate IP addresses. Unless you are very careful and have good documentation, its easy to have misconfigured devices and have IP conflicts. Also check your DHCP pool does not overlap with any statically configured hosts.