iptraf: 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/iptraf - from package: iptraf

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

On Debian possible default full paths are:

/usr/sbin/iptraf - from package: iptraf

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

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