redir6: 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/redir6 - from package: thc-ipv6

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

Error in other languages:
redir6: bevel nie gevind nie
redir6: comandă negăsită
redir6: comando não encontrado
redir6: commande introuvable
redir6: command not found
redir6: käsku ei ole
redir6: không tìm thấy lệnh
redir6: komanda nerasta
redir6: Kommando nicht gefunden.
redir6: kommandot finns inte
redir6: komut yok
redir6: nie znaleziono polecenia
redir6: níor aimsíodh an t-ordú
redir6: no se encontró la orden
redir6: no s'ha trobat l'ordre
redir6: opdracht niet gevonden
redir6: parancs nem található
redir6: perintah tidak ditemukan
redir6: príkaz nenájdený
redir6: příkaz nenalezen
redir6: команда не найдена
redir6: командата не е открита
redir6: 命令找不到
redir6: コマンドが見つかりません