Conexão FTP via Load Balancer cd funciona ls falha

Question

Abaixo está a configuração.

Client is a linux server IP: 10.204.21.143. This server is only reachable to HA Proxy server.

HA Proxy Server IP: 10.204.24.71 (Its a Solaris 11.3 Server) 

Back end Server where the FTP Server is running : 10.212.22.31 This server is only reachable to HA Proxy Server only and not to Client Server.

Configuração de proxy HA:

$ cat haproxy.cfg
global
      maxconn 15000
      pidfile dmshaproxy.pid
      daemon
      stats socket dmshaproxy.sock mode 0600 level admin
      spread-checks 5

defaults
      mode tcp
      retries 3
      maxconn 15000
      contimeout 5s
      clitimeout 300s
      srvtimeout 300s
      option contstats

listen FTP 10.204.24.71:2121
    server ftp-serv00 10.212.22.31:21 check inter 20s
$

Agora posso me conectar a partir do cliente, executar o comando cd e ele funciona. mas o ls não funciona.

[root@qa-lt143 ~]# ftp 10.204.24.71 2121
Connected to 10.204.24.71 (10.204.24.71).
220 ::ffff:10.212.22.31 FTP server ready
Name (10.204.24.71:root): oracle
331 Password required for oracle
Password:
230 User oracle logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> cd RMAN_BKP
250 CWD command successful
ftp> pwd
257 "/export/home/oracle/RMAN_BKP" is the current directory
ftp> ls
227 Entering Passive Mode (10,212,22,31,137,99).    <--- This IP is of backend server. but it should be of HA-Proxy Server. Not sure why its taking the backend server.
ftp: connect: Connection timed out
ftp>

Eu vejo que quando eu faço ls toma o ip de back-end para conectar o que não é alcançável a partir do servidor do cliente. Não sei por que não está usando o IP do servidor HA-Proxy.

Também tentei o mesmo com a conexão ativa e também não funcionou. Desta vez, levou o IP do seu servidor local.

[root@qa-lt143 ~]# ftp -A 10.204.24.71 2121
Connected to 10.204.24.71 (10.204.24.71).
220 ::ffff:10.212.22.31 FTP server ready
Name (10.204.24.71:root): oracle
331 Password required for oracle
Password:
230 User oracle logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> cd RMAN_BKP
250 CWD command successful
ftp> pwd
257 "/export/home/oracle/RMAN_BKP" is the current directory
ftp> ls
500 Illegal PORT command
ftp: bind: Address already in use
ftp> debug
Debugging on (debug=1).
ftp> ls
---> PORT 10,204,21,143,180,120
500 Illegal PORT command
ftp>

Por favor, ajude.