A local IP address (RFC 1918) on my network that is not … local

I've noticed an IP address today on my network (192.168.15.1) which when visited actually goes to a page that has a router webconfig page (Not my router)

The puzzling thing is that i tried traceroute 192.168.15.1 which said that the distance between me and that host is 9 hops, whereas the distance between me and any other computer on my home network is 2 hops away
(My computer --> Router --> Host)

Can someone please explain what's going on here ?

tracert output:

Tracing route to 192.168.15.1 over a maximum of 30 hops

  1    <1 ms    <1 ms    <1 ms  192.168.1.1
  2    47 ms    51 ms    49 ms  [163.121.171.123]
  3     *        *        *     Request timed out.
  4   128 ms     *        *     163.121.211.134.dnet.net [163.121.211.134
]
  5     *      134 ms   126 ms  10.37.242.18
  6    94 ms    90 ms    95 ms  10.35.2.157
  7   178 ms   254 ms   206 ms  10.32.8.107
  8    85 ms    57 ms   318 ms  10.35.0.186
  9   215 ms   241 ms   230 ms  192.168.15.1

Trace complete.

Solution 1:

Your subnet mask is undoubtedly 255.255.255.0, so that address is not on your network. If your subnet mask is 255.255.0.0, your machine wouldn't be sending traffic to it through your gateway.