tracert6: 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/tracert6 - from package: ndisc6

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

On Debian possible default full paths are:

/usr/bin/tracert6 - from package: ndisc6

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

Error in other languages:
tracert6: bevel nie gevind nie
tracert6: comandă negăsită
tracert6: comando não encontrado
tracert6: commande introuvable
tracert6: command not found
tracert6: käsku ei ole
tracert6: không tìm thấy lệnh
tracert6: komanda nerasta
tracert6: Kommando nicht gefunden.
tracert6: kommandot finns inte
tracert6: komut yok
tracert6: nie znaleziono polecenia
tracert6: níor aimsíodh an t-ordú
tracert6: no se encontró la orden
tracert6: no s'ha trobat l'ordre
tracert6: opdracht niet gevonden
tracert6: parancs nem található
tracert6: perintah tidak ditemukan
tracert6: príkaz nenájdený
tracert6: příkaz nenalezen
tracert6: команда не найдена
tracert6: командата не е открита
tracert6: 命令找不到
tracert6: コマンドが見つかりません