Keepalived não re-adicionando servidores reais

Question

Estou tentando configurar um servidor virtual simples no Keepalived e, quando os servidores são removidos do pool, eles não são adicionados novamente automaticamente. No syslog do servidor Keepalived, vejo:

Oct 01 11:37:39 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:40 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:40 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:41 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:44 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:47 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:48 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:48 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:49 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:49 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:50 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:50 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:51 lb2 kernel:  IPVS: WRR: no destination available: no destinations present
Oct 01 11:37:51 lb2 kernel:  IPVS: WRR: no destination available: no destinations present

saídas ipvsadm:

[ashinn@lb2 ~]$ sudo ipvsadm

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
FWM  700000 wrr persistent 300

Aqui está a parte relevante do keepalived.conf:

virtual_server fwmark 700000 {
    delay_loop 20
    lb_algo wrr
    lb_kind NAT
    persistence_timeout 300
    protocol TCP

    real_server 10.10.35.11 443 {
        weight 24
        SSL_GET {
            url {
                path /check.php
            }
        }
    }

    real_server 10.10.35.12 443 {
        weight 24
        SSL_GET {
            url {
                path /check.php
            }
        }
    }
}

O servidor Keepalived pode, de fato, alcançar os servidores reais:

[ashinn@lb2 ~]$ curl -k https://10.10.35.11/check.php
FAIL<br/>
/usr/bin/mencoder is not executable.<br/>
dio extension is not loaded.<br/>

Alguma idéia de por que os servidores não são adicionados novamente depois de removidos?