how 2 find DNS and Gateway of Other IPs

Hi! i dont hav a high knowledge about Networking.but guys plzz try 2
help me. my IP address is 172.1.28.26 n GW is 172.1.28.1. i scanned al
the IPs os this Rnage i.e. 172.1.28.x. so i saw many users still using
this Range.But i m not able 2 Ping the Gateway. i think the GW is
changed or the DNS. i dont know exactly what has been changed. nut i
want 2 know which GW n DNS thse users r using now.i m able 2 fing their
MAC address n IP through a Scanner. plzz help me fing their DNS &
GAteWay. thnx in advance.

.