ubuntu 14下的多网卡绑定配置 ：报错

ubuntu 14.04 lts server，有多个网卡（4块网卡，2块插了网线），安装搜索的各种教程配置绑定：

auto lo
iface lo inet loopback
 
auto em2
iface em2 inet static
 address 172.16.1.1
 netmask 255.255.255.0
 
 auto em5
 iface em5 inet static
 address 172.16.1.2
 netmask 255.255.255.0
 
 iface bond0 inet static
 address 172.16.1.11
 netmask 255.255.255.0
 network 172.16.1.0
 broadcast 172.16.1.255
 gateway 172.16.1.254
 dns-nameservers 8.8.8.8
 up ifenslave bond0 em2 em5
 down ifenslave -d bond0 em2 em5

cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v3.7.1 (April 27, 2011)
Bonding Mode: load balancing (round-robin)
MII Status: down
MII Polling Interval (ms): 100
Up Delay (ms): 0
Down Delay (ms): 0