hping2: 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/sbin/hping2 - from package: hping3

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

Error in other languages:
hping2: bevel nie gevind nie
hping2: comandă negăsită
hping2: comando não encontrado
hping2: commande introuvable
hping2: command not found
hping2: käsku ei ole
hping2: không tìm thấy lệnh
hping2: komanda nerasta
hping2: Kommando nicht gefunden.
hping2: kommandot finns inte
hping2: komut yok
hping2: nie znaleziono polecenia
hping2: níor aimsíodh an t-ordú
hping2: no se encontró la orden
hping2: no s'ha trobat l'ordre
hping2: opdracht niet gevonden
hping2: parancs nem található
hping2: perintah tidak ditemukan
hping2: príkaz nenájdený
hping2: příkaz nenalezen
hping2: команда не найдена
hping2: командата не е открита
hping2: 命令找不到
hping2: コマンドが見つかりません