dnsperf: 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/dnsperf - from package: dnsperf

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

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