jumbo6: 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:

/usr/sbin/jumbo6 - from package: ipv6toolkit

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

Error in other languages:
jumbo6: bevel nie gevind nie
jumbo6: comandă negăsită
jumbo6: comando não encontrado
jumbo6: commande introuvable
jumbo6: command not found
jumbo6: käsku ei ole
jumbo6: không tìm thấy lệnh
jumbo6: komanda nerasta
jumbo6: Kommando nicht gefunden.
jumbo6: kommandot finns inte
jumbo6: komut yok
jumbo6: nie znaleziono polecenia
jumbo6: níor aimsíodh an t-ordú
jumbo6: no se encontró la orden
jumbo6: no s'ha trobat l'ordre
jumbo6: opdracht niet gevonden
jumbo6: parancs nem található
jumbo6: perintah tidak ditemukan
jumbo6: príkaz nenájdený
jumbo6: příkaz nenalezen
jumbo6: команда не найдена
jumbo6: командата не е открита
jumbo6: 命令找不到
jumbo6: コマンドが見つかりません