ifirewall: 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/ifirewall - from package: ipmiutil

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

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