如何监听非本地IP

做HA的时候，如果每个机器上同时需要监听多个IP的同一个端口。那么肯定是需要写死监听的IP和端口。
比如在haproxy里面：

  
frontend free  
bind 10.17.10.4:80  
default_backend test1  
frontend free  
bind 10.17.10.5:80  
default_backend test2

backend test1  
mode http  
balance leastconn  
option  httpchk  
cookie SERVERID insert indirect  nocache maxidle 10m maxlife 8h  
option forwardfor header ORIG_CLIENT_IP  
option  httpclose  
server  free174 10.253.4.16:8080 weight 10 rise 3 fall 5 check inter 2000 cookie apm1174  
server  free173 10.253.4.15:8080 weight 10 rise 3 fall 5 check inter 2000 cookie apm1173

backend test2  
mode http  
balance leastconn  
option  httpchk  
cookie SERVERID insert indirect  nocache maxidle 10m maxlife 8h  
option forwardfor header ORIG_CLIENT_IP  
option  httpclose  
server  free174 10.253.3.16:8080 weight 10 rise 3 fall 5 check inter 2000 cookie apm1174  
server  free173 10.253.3.15:8080 weight 10 rise 3 fall 5 check inter 2000 cookie apm1173

主机和备机都要同时先启动好haproxy，但是备机在未获得这个IP前是无法启动haproxy的。这时可以通过修改内核参数来绑定非本地地

  
echo 1 > /proc/sys/net/ipv4/ip_nonlocal_bind