subnetcalc: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/subnetcalc - from package: subnetcalc

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/subnetcalc - from package: subnetcalc

You may install the required package with command apt-get install {package}

Error in other languages:
subnetcalc: bevel nie gevind nie
subnetcalc: comandă negăsită
subnetcalc: comando não encontrado
subnetcalc: commande introuvable
subnetcalc: command not found
subnetcalc: käsku ei ole
subnetcalc: không tìm thấy lệnh
subnetcalc: komanda nerasta
subnetcalc: Kommando nicht gefunden.
subnetcalc: kommandot finns inte
subnetcalc: komut yok
subnetcalc: nie znaleziono polecenia
subnetcalc: níor aimsíodh an t-ordú
subnetcalc: no se encontró la orden
subnetcalc: no s'ha trobat l'ordre
subnetcalc: opdracht niet gevonden
subnetcalc: parancs nem található
subnetcalc: perintah tidak ditemukan
subnetcalc: príkaz nenájdený
subnetcalc: příkaz nenalezen
subnetcalc: команда не найдена
subnetcalc: командата не е открита
subnetcalc: 命令找不到
subnetcalc: コマンドが見つかりません