ripd: 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/sbin/ripd - from package: quagga

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

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