ipv4calc: 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/ipv4calc - from package: perl-Net-IPv4Addr

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

On Debian possible default full paths are:

/usr/bin/ipv4calc - from package: libnetwork-ipv4addr-perl

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

Error in other languages:
ipv4calc: bevel nie gevind nie
ipv4calc: comandă negăsită
ipv4calc: comando não encontrado
ipv4calc: commande introuvable
ipv4calc: command not found
ipv4calc: käsku ei ole
ipv4calc: không tìm thấy lệnh
ipv4calc: komanda nerasta
ipv4calc: Kommando nicht gefunden.
ipv4calc: kommandot finns inte
ipv4calc: komut yok
ipv4calc: nie znaleziono polecenia
ipv4calc: níor aimsíodh an t-ordú
ipv4calc: no se encontró la orden
ipv4calc: no s'ha trobat l'ordre
ipv4calc: opdracht niet gevonden
ipv4calc: parancs nem található
ipv4calc: perintah tidak ditemukan
ipv4calc: príkaz nenájdený
ipv4calc: příkaz nenalezen
ipv4calc: команда не найдена
ipv4calc: командата не е открита
ipv4calc: 命令找不到
ipv4calc: コマンドが見つかりません