For the moment a telemetry gateway and the site router refuse to talk and IT is a text message away: enter both devices' IP and mask, and find out whether they're even on the same network. Runs entirely offline; inputs persist in this browser via localStorage.
How the Answer Is Derived
What a subnet mask actually does
An IP address is 32 bits. The mask splits it into a network part and a host part: wherever the mask has a 1-bit, that bit belongs to the network number. Two devices can talk directly only if their network numbers match — otherwise each one sends the traffic to its gateway and hopes. The math is one bitwise AND per device:
network = IP & mask
Example: 192.168.17.1 & 255.255.255.0 = 192.168.17.0, while 10.215.113.50 & 255.255.255.0 = 10.215.113.0. Different network numbers — the devices are invisible to each other without a router that knows both networks.
The usual field fix
Fastest: give the laptop a second static IP in the device's subnet (most OSes allow multiple addresses per adapter) — you keep internet on the site network and reach the device directly.
Right answer long-term: have IT add a route or put the device VLAN behind the router. That's their call, not a field improvisation.
Matching subnets is necessary, not sufficient — if the two devices are on physically separate switches or separate VLANs, they still can't talk. This tool answers the addressing question only.
Reading the numbers you were handed
/24 after an address is the same thing as mask 255.255.255.0 — the number counts the 1-bits. The tool accepts either form.
Addresses starting 10.x, 172.16–31.x, and 192.168.x are private ranges (RFC 1918) — normal for industrial gear, never reachable from the internet directly.
A non-contiguous mask (1-bits with gaps) is almost certainly a typo; the tool flags it.
References
RFC 1918 — Address Allocation for Private Internets. https://www.rfc-editor.org/rfc/rfc1918
The site's IT/OT network administrator — the governing authority for anything beyond reading addresses.