tcpprep: 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/tcpprep - from package: tcpreplay

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

On Debian possible default full paths are:

/usr/bin/tcpprep - from package: tcpreplay

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

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