network_traffic: 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/network_traffic - from package: libstatgrab-examples

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

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