Many network devices that need to be discovered on the network use the so called 'Bonjour' protocol. Bonjour locates devices such as camera, printers, other computers, and the services that those devices offer on a local network using multicast Domain Name System (mDNS) service records. Most cameras will respond to this multicast.
Network discovery tools from different vendors use this technique to discover specific brands of devices (cameras). They build their vendor specific applications on top of this, and only cameras of that specific brand are presented.
However, there are 'generic' Bonjour tools, that will discover ALL devices that are on the local subnet, and support Bonjour.
A free piece of software is 'Bonjour SDK for Windows'
Bonjour SDK for Windows is intended to be used to develope your own applications https://developer.apple.com/bonjour/index.html
However if you just install 'Bonjour SDK for Windows' it also installs a plug-in for Internet Explorer.
This plug-in for Internet Explorer is a very handy tool to dicover your cameras.
In the IE toolbar, you should see the Bonjour icon (a swirling icon), and if you click on it, on the left will open a toolbar, listing ALL the cameras, printers and services found on the network. Clicking on the device will open the web interface of the device in the IE window. This allows you to access the device web interface, without even knowing it's current IP address. See below:
Note that most devices are DCHP per default, so provided there is a DHCP server on the network, you can directly access the device by clicking on its name in the Bonjour toolbar. In the network configuration, you can then give it a fixed IP address if desired.