场景说明：目前在CentOS版本上进行网桥br0到普通网络的配置eth0,发现如下的一个问题
ifconfig

br0       Link encap:Ethernet  HWaddr 00:0C:29:5D:07:15  

          inet addr:192.168.40.250  Bcast:192.168.40.255  Mask:255.255.255.0

          inet6 addr: fe80::20c:29ff:fe5d:715/64 Scope:Link

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:290 errors:0 dropped:0 overruns:0 frame:0

          TX packets:10 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:0 

          RX bytes:18299 (17.8 KiB)  TX bytes:636 (636.0 b)

eth0      Link encap:Ethernet  HWaddr 00:0C:29:5D:07:15  

          inet addr:192.168.40.250  Bcast:192.168.40.255  Mask:255.255.255.0

          inet6 addr: fe80::20c:29ff:fe5d:715/64 Scope:Link

          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

          RX packets:49743 errors:0 dropped:0 overruns:0 frame:0

          TX packets:404 errors:0 dropped:0 overruns:0 carrier:0

          collisions:0 txqueuelen:1000 

          RX bytes:3793317 (3.6 MiB)  TX bytes:157382 (153.6 KiB)

          Interrupt:19 Base address:0x2024 

# ethtool br0

Settings for br0:

Link detected: yes

# ethtool eth0

Settings for eth0:

Supported ports: [ TP ]

Supported link modes:   1000baseT/Full 

Supported pause frame use: No

Supports auto-negotiation: No

Advertised link modes:  Not reported

Advertised pause frame use: No

Advertised auto-negotiation: No

Speed: 1000Mb/s

Duplex: Full

Port: Twisted Pair

PHYAD: 0

Transceiver: internal

Auto-negotiation: off

MDI-X: Unknown

Link detected: yes

重启网络：service network restart

第一次尝试失败，