sip-redirect: 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/sip-redirect - from package: sip-redirect

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

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