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I'm trying to clear something up that I haven't been able to get a simple answer to. If I have multiple computers on the same wifi network, is it correct that they will have the same network ID, but different host IDs? For example for a class C ip address of 123.123.123.12, would the first 3 bytes be the same for a different computer on the same wifi, for example 123.123.123.14? Thank you!

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    "For example for a class C ip address of 123.123.123.12" First, network classes are dead (please let them rest in peace), killed in 1993 (before the Internet went commercial in 1995) by RFCs 1517, 1518, and 1519, which defined CIDR (Classless Inter-Domain Routing). Modern networking does not use network classes. Second, under the (deprecated) network classes, 123.123.123.12 was a Class A address, not a Class C address as you say. – Ron Maupin Nov 25 '19 at 20:56
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If I have multiple computers on the same wifi network, is it correct that they will have the same network ID, but different host IDs?

Often, but not necessarily. A WLAN operates at L2, so it really doesn't have any direct correlation to IP addresses. When a client connects to an AP, the AP in many ways (but by no means all) can be considered a switch of sorts. Let me give some fairly common examples of how devices connected to the same WLAN may have different L3 networks.

So to begin with there is the VLAN assigned to a client devices. In many wireless networks, this will be a simple WLAN->VLAN mapping and all client devices will be considered part of the same VLAN. However it is also possible to assign different devices to different VLANs even if they are connected to the same WLAN. In these cases, the clients likely won't be all sharing the same L3 network.

Additionally, a L2 VLAN can have multiple L3 IPv4 networks assigned to it. Again, in these cases the clients likely won't be all sharing the same L3 network.

Finally, if the WLAN has both IPv4 and IPv6 enabled, clients may be part of either or both L3 networks. So if a device is only IPv6, it won't be sharing the same L3 network with any device that is IPv4 only.

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Usually, but not necessarily. A Wi-Fi network (sometimes called a WLAN) is the functional equivalent of a VLAN. In other words, it's a layer 2 construct, that has no concept of IP addresses. Usually, there is a one-to-one mapping between VLANs (or WLANs) and subnets, but not always.

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Generally if you are connected to the same WLAN SSID as another device then yes your devices will have the same network/subnet ID. This is because WLANs are usually designated to a specific VLAN.

There are options most Wireless products support to further segment out Wireless clients from each other. So if you’re on a Guest Wireless LAN and Station Separation is enabled, your devices can be on the same VLAN/subnet but wont communicate with one another.

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