New Version backend config

[ll]

hi，all，Is there any change about the muti-backend config in the varnish-cache-2.1.4 version ?
I set the backend like that
backend abc {
         .host="www.abc.com";
         .port="80";
}
the www.abc.com DNS had change to my varnish server ip 192.168.1.1
and i had edit the varnish server 's /etc/hosts file ,add
192.168.1.2 www.abc.com

but now, all the url which had set the backend to "abc" is not work.I use the same config in the 
2.0.4 version is fine. I don't know how to fix it ?