Two Computers Cannot See Each Other Different Subnet Fix
Same switch, same room, working internet on both — and zero connection between two PCs. This page walks the different-subnet diagnosis step by step, because this fault hides behind healthy-looking hardware.
✍️ Technical Anshu🪟 Windows 10 / 11⏱️ 6 minute read
🎥 Full video — see how the mask decides who is on your street
This is one of the most misdiagnosed faults in small offices. Cables get changed, Windows gets reinstalled, and the real cause — two addresses from two different streets — sits quietly in ipconfig the whole time. Here is how to spot it in two minutes.
Two healthy PCs that still cannot talk (example values)
PC A — everything looks fine
IP address192.168.1.25
Subnet mask255.255.255.0
PC B — also looks fine
IP address192.168.2.30
Subnet mask255.255.255.0
The hidden truth
PC A street192.168.1
PC B street192.168.2 — a different street
☝️ Both PCs have internet and no error anywhere — but to each of them, the other PC lives 'outside', beyond the gateway.
1
The Symptom That Gives It Away
The classic report sounds impossible: both PCs are plugged into the same switch, both have working internet, no cable is faulty — yet neither can open the other's shared folder, and pinging each other times out. When every piece of hardware checks out, suspect the addresses themselves: the two PCs are on different subnets, and each is trying to reach the other through the gateway instead of directly.
2
The Two-Minute Diagnosis
On both PCs, run ipconfig
Write down each address and mask side by side
Apply the mask: with 255.255.255.0, compare the first three numbers
If the first three numbers differ — 192.168.1.x versus 192.168.2.x — you have found it. Different streets.
Also compare the masks themselves. A PC with mask 255.255.0.0 sees a much bigger street than its neighbour with 255.255.255.0, so one may reach the other while the return path fails — the maddening 'works one way only' version of the same fault.
3
How PCs End Up on Different Streets
Nobody usually chooses this; it creeps in:
A second router was plugged in to 'add Wi-Fi', and its DHCP started handing out a different range (192.168.2.x or 192.168.0.x)
A PC kept a hand-typed static address from an old office or an old router
The main router was replaced and the new one's default range differs from the old one — half the devices renewed, half kept old leases
4
The Fix — One Street, One DHCP
The cure is to bring every device back to one street served by one DHCP server:
Decide the single range, usually the main router's, such as 192.168.1.x
Set wrongly-addressed PCs back to Obtain an IP address automatically, or correct their static entries to the chosen street
If a second router exists, disable its DHCP (or set it to access-point mode) so only one receptionist assigns rooms
On each changed PC, run ipconfig /renew, then test both ways: ping each other and open the share
Test the return direction too — sharing that works one way only means one PC's mask or address is still off.
🎥 Watch the Full Video
The video explains the street picture behind this fault — once you see it, the ipconfig comparison becomes obvious.
Why can two PCs on the same switch not see each other?
Usually because their IP addresses are on different subnets — for example 192.168.1.25 and 192.168.2.30 with mask 255.255.255.0. Each PC treats the other as an outside address and sends traffic to the gateway instead of directly. Comparing ipconfig on both PCs reveals it immediately.
Both PCs have internet, so how can the network be wrong?
Internet traffic always goes through the gateway, so it works from any subnet that the router serves. Local delivery is different — it depends on both PCs agreeing they are on the same subnet. That is why the internet can be perfect while sharing is completely broken.
A second router was added for Wi-Fi. Could that cause this?
Yes — it is the most common cause. A second router with its DHCP still on hands out addresses from its own range, splitting one office into two streets. The fix is to disable DHCP on the second router or switch it to access-point mode, leaving one DHCP server for the whole network.
This guide is based on the Technical Anshu video on IP, DNS, gateway and subnet mask • Stuck on a step? Ask in the video comments — you will get an answer there 🙏