I have used PingPlotter for years, generally very happily. But today I hit a puzzle I've not seen before.

From a LAN behind a router, when tracing to a site on the internet, the first hop is always, so far as I can remember, the router/gateway. So on subnet 192.168.100.0/24, the first hop is generally 192.168.100.1.

But today, on a LAN that is behind router A, which in turn is downstream from an LTE modem/router B, PingPlotter skips the router A gateway address, and shows router B's gateway address as the first hop.

So where the LAN subnet is 192.168.100.0/24, and the link between router A and LTE modem is 192.168.0.xx, PingPlotter shows the first hop as 192.168.0.1.

PingPlotter is happy to show pings from 192.168.100.1 if you enter that destination specifically (and, no surprise, just one hop is shown). But if you enter 192.168.0.1 as the destination, then you still get only one hop, to 192.168.0.1.

For what it's worth, the PC running PingPlotter has address 192.168.100.30, and shows a gateway address of 192.168.100.1.

I have tried this with latest version PingPlotter, and also v3.5.something. Same result.

Any ideas on why this happens? Thanks.