LVS NAT 模式 后端realserver 不稳定，求原因。

LVS NAT模式 备现在不稳定，经常有realserver掉线，目前realserver有20多台。

Dec 4 11:51:35 backup Keepalived_healthcheckers: TCP connection to [192.168.1.165:80] failed !!!
Dec 4 11:51:35 backup Keepalived_healthcheckers: Removing service [192.168.1.165:80] from VS [212.151.11.12:80]
Dec 4 11:51:35 backup Keepalived_healthcheckers: Remote SMTP server [127.0.0.1:25] connected.
Dec 4 11:51:35 backup Keepalived_healthcheckers: SMTP alert successfully sent.
Dec 4 11:51:41 backup Keepalived_healthcheckers: TCP connection to [192.168.1.165:80] success.
Dec 4 11:51:41 backup Keepalived_healthcheckers: Adding service [192.168.1.165:80] to VS [212.151.11.12:80]
Dec 4 11:51:41 backup Keepalived_healthcheckers: Remote SMTP server [127.0.0.1:25] connected.
Dec 4 11:51:41 backup Keepalived_healthcheckers: SMTP alert successfully sent.

用tcpdump抓包发现很多这样的信息，主上没有， realserver都是192.168.1.X网段
13:24:28.057918 IP 192.168.1.55.tlisrv > 192.168.1.15.microsoft-ds: P 75384:75490(106) ack 409175 win 65097
13:24:28.058560 IP 192.168.1.55.tlisrv > 192.168.1.15.microsoft-ds: P 75490:75566(76) ack 409314 win 64958
13:24:28.058957 IP 192.168.1.55.tlisrv > 192.168.1.15.microsoft-ds: P 75566:75642(76) ack 409418 win 64854
13:24:28.059212 IP 192.168.1.55.tlisrv > 192.168.1.15.microsoft-ds: P 75642:75718(76) ack 409506 win 64766
13:24:28.059922 IP 192.168.1.55.tlisrv > 192.168.1.15.microsoft-ds: P 75718:75763(45) ack 409574 win 64698
13:24:28.063471 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 62638:62786(148) ack 336091 win 65347
13:24:28.063975 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 62786:62934(148) ack 336195 win 65243
13:24:28.064709 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 62934:63082(148) ack 336315 win 65123
13:24:28.065119 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63082:63230(148) ack 336419 win 65019
13:24:28.065554 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63230:63378(148) ack 336507 win 64931
13:24:28.066085 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63378:63536(158) ack 336611 win 64827
13:24:28.066583 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63536:63612(76) ack 336750 win 64688
13:24:28.067082 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63612:63688(76) ack 336822 win 64616
13:24:28.067321 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63688:63808(120) ack 336926 win 64512
13:24:28.067684 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63808:63871(63) ack 336990 win 64448
13:24:28.070144 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63871:63947(76) ack 337079 win 64359
13:24:28.070502 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63947:63992(45) ack 337167 win 64271
13:24:28.070833 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 63992:64150(158) ack 337206 win 64232
13:24:28.071311 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 64150:64226(76) ack 337345 win 64093
13:24:28.071348 IP 192.168.1.56.cbserver > 192.168.1.15.microsoft-ds: P 96649:96755(106) ack 581153 win 65097
13:24:28.071726 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 64226:64271(45) ack 337449 win 65535
13:24:28.071929 IP 192.168.1.56.cbserver > 192.168.1.15.microsoft-ds: P 96755:96831(76) ack 581292 win 65535
13:24:28.072080 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 64271:64429(158) ack 337488 win 65496
13:24:28.072233 IP 192.168.1.56.cbserver > 192.168.1.15.microsoft-ds: P 96831:96907(76) ack 581396 win 65431
13:24:28.072485 IP 192.168.1.56.cbserver > 192.168.1.15.microsoft-ds: P 96907:96983(76) ack 581484 win 65343
13:24:28.072668 IP 192.168.1.68.eoss > 192.168.1.15.microsoft-ds: P 64429:64492(63) ack 337627 win 65357
13:24:28.072845 IP 192.168.1.56.cbserver > 192.168.1.15.microsoft-ds: P 96983:97028(45) ack 581552 win 65275