iptables: 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 Debian possible default full paths are:

/sbin/iptables - from package: iptables

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

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