Ftp – HAproxy for load balancing vsFTPd servers

I have successfully set up a load balancing environment using HAProxy and 2 FTP servers running vsftpd. This is what the setup looks so far:

Proxy: ftp00 | 192.168.2.135 (public, eth0) | 10.11.130.1 (private, eth1)
Node01: ftp01 | 10.11.130.140
Node02: ftp02 | 10.11.130.141

Operating system: CentOS 6.6
HA-Proxy: version 1.5.2 2014/07/12
vsftpd: version 2.2.2

ftp00: /etc/haproxy/haproxy.conf

#---------------------------------------------------------------------
# GLOBAL CONFIG
#---------------------------------------------------------------------
global
    daemon
    log         127.0.0.1 local0 info
    log         127.0.0.1 local1 notice
    log         127.0.0.1 local5 debug
    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy

    # turn on stats unix socket
    stats socket /var/lib/haproxy/stats

#---------------------------------------------------------------------
# DEFAULTS CONFIG
#---------------------------------------------------------------------
defaults
        log             global
        mode            tcp
        option          tcplog
        option          dontlognull
        retries         3
        option          redispatch
        option          tcpka
        maxconn         2000
        contimeout      5000

#---------------------------------------------------------------------
# POOL CONFIG
#---------------------------------------------------------------------
listen ftp-lb
        bind 192.168.2.135:21
        mode tcp
        option tcplog
        balance roundrobin
        server ftp01 10.11.130.140:21 weight 10 minconn 30 maxconn 1000 check
        server ftp02 10.11.130.141:21 weight 10 minconn 30 maxconn 1000 check

#---------------------------------------------------------------------
# HAPROXY DASHBOARD CONFIG
#---------------------------------------------------------------------
listen stats
    bind 192.168.2.135:81
    mode http
    stats enable
    stats refresh 30s
    stats show-node
    stats uri  /stats
    stats auth admin:password

ftp00: /etc/sysconfig/iptablesfound [here]

*nat
:PREROUTING ACCEPT [7:724]
:POSTROUTING ACCEPT [5:300]
:OUTPUT ACCEPT [5:300]
-A PREROUTING -d 192.168.2.135/32 -i eth1 -p tcp -m tcp --dport 12001:14000 -j DNAT --to-destination 10.11.130.140
-A PREROUTING -d 192.168.2.135/32 -i eth1 -p tcp -m tcp --dport 16001:18000 -j DNAT --to-destination 10.11.130.141
-A POSTROUTING -s 10.11.130.140/32 -o eth1 -j SNAT --to-source 192.168.2.135
-A POSTROUTING -s 10.11.130.141/32 -o eth1 -j SNAT --to-source 192.168.2.135
COMMIT
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [732:64731]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 21 -j ACCEPT
-A INPUT -p tcp -m state --state NEW -m tcp --dport 81 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

ftp01: /etc/vsftpd/vsftpd.conf

#------------------------------------------
# GENERAL CONFIG
#------------------------------------------
anonymous_enable=NO
local_enable=YES
write_enable=YES
local_umask=022
dirmessage_enable=YES
pam_service_name=vsftpd

#------------------------------------------
# LOG CONFIG
#------------------------------------------
xferlog_enable=YES
xferlog_std_format=NO
log_ftp_protocol=YES

#------------------------------------------
# USER WHITELIST
#------------------------------------------
userlist_enable=YES
userlist_deny=NO
userlist_file=/etc/vsftpd/user_list

#------------------------------------------
# PASSIVE MODE CONFIG
#------------------------------------------
#tcp_wrappers=YES
pasv_enable=YES
port_enable=YES
pasv_min_port=12001
pasv_max_port=14000
pasv_address=192.168.2.135
pasv_addr_resolve=NO
connect_from_port_20=YES

#------------------------------------------
# Added listen address for internal only
#------------------------------------------
listen=YES
listen_address=10.11.130.140

#-----------------------------------------
# BANNER CONFIG
#-----------------------------------------
banner_file=/etc/vsftpd/issue

ftp01: /etc/sysconfig/iptables

*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -p tcp -m state --state NEW -m tcp -m multiport --dports 12001:14000 -j ACCEPT
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 20 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

ftp02: /etc/vsftpd/vsftpd.conf

Difference to ftp01 config:

pasv_min_port=16001
pasv_max_port=18000

listen_address=10.11.130.141

ftp02: /etc/sysconfig/iptables

Same as **ftp01** with respective port ranges

all nodes: /etc/sysconfig/iptables-config

IPTABLES_MODULES="nf_conntrack_ftp"

SELinux is deactivated on all machines. I've followed several tutorials (like this, and this), but I still can't get passive mode to work. I can log in to the FTP servers via the HAproxy load balancer (which is set to roundrobin and this also works), and it keeps giving me this:

220-***FTP SERVER CLUSTER NODE 02***
220
Name (192.168.2.135:root): root
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
227 Entering Passive Mode (192,168,2,135,67,94).
ftp: connect: Connection timed out
ftp>

Since I've gone through all I can think of and almost everything that's out there dealing with this, I am getting a little frustrated. My configuration is built identically to those in the tutorials, but it just won't work. Maybe I am missing out on something that I didn't notice yet, so any help is much appreciated!

At least the port number seems to be correct. ftp02 is set up to use 16001 - 18000, and entering passive mode uses 67*256 + 94 = 17246, which is totally fine.