dfrouter: 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/bin/dfrouter - from package: sumo

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

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