rlm_ippool_tool: 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/rlm_ippool_tool - from package: freeradius-utils

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

On Debian possible default full paths are:

/usr/bin/rlm_ippool_tool - from package: freeradius-utils

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

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