@echo off
setlocal enabledelayedexpansion

for /l %%i in (2,1,100) do (
    set "ip=10.1.2.%%i"
    ping -n 1 !ip! > nul
    if !errorlevel! equ 0 (
        echo !ip! is reachable
    ) else (
        echo !ip! is not reachable
    )
)

endlocal
pause