VS/TUN方式的FTP无法正常连接

前几次提问都没有得到很满意的答复，这次的问题持续太久，希望能得到章博士的帮助。

LVS的分布：
VIP:192.168.170.250
DIRECTOR:192.168.170.252
RS1:192.168.170.253
RS2:192.168.171.253
（说明：由于唯一的一台RS的性能不好，而且带宽限制，所以用了4块网卡，作了2个bond。目的是负载均衡、加倍带宽）

Director 的配置：
echo "3" > /proc/sys/net/ipv4/tcp_syn_retries
echo "1" >/proc/sys/net/ipv4/ip_forward

-A -t 192.168.170.250:21 -s wlc -p 1000
-a -t 192.168.170.250:21 -r 127.0.0.1:21 -g -w 1
-a -t 192.168.170.250:21 -r 192.168.170.253:21 -i -w 0
-a -t 192.168.170.250:21 -r 192.168.171.253:21 -i -w 0

Realserver的配置：
insmod /usr/local/lib/modules/2.4.29/local/noarp.o
echo '1' > /proc/sys/net/ipv4/ip_forward
echo '0' > /proc/sys/net/ipv4/conf/all/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/default/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/lo/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/eth0/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/eth1/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/eth2/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/eth3/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/tunl0/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/bond0/rp_filter
echo '0' > /proc/sys/net/ipv4/conf/bond1/rp_filter

noarpctl add 192.168.170.250 192.168.170.253

在DIRECTOR上tcpdump抓包的结果：
14:13:43.244749 IP (tos 0x0, ttl 125, id 11235, offset 0, flags [DF], proto: TCP (6), length: 48) 192.168.168.201.2029 > FTP_Server.ftp: S, cksum 0xc64e (correct), 2203525498:2203525498(0) win 65535


在RS上tcpdump抓包的结果：
16:04:04.004716 IP (tos 0x0, ttl 125, id 11851, offset 0, flags [DF], proto: TCP (6), length: 48) 192.168.168.201.2044 > FTP-SERVER.ftp: S, cksum 0xfee0 (correct), 1511002656:1511002656(0) win 65535