环境：RedHat Enterprise Linux 5.X
现象：使用ifconfig命令查看网卡信息，发现有virbr0、xenbr0等多余的信息，如下：
[root@EXFO ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:64:C4:80
inet addr:XXX.XX.XX.XX Bcast:XXX.XX.XX.XX Mask:255.255.255.192
inet6 addr: fe80::20c:29ff:fe64:c480/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:4510 errors:0 dropped:0 overruns:0 frame:0
TX packets:300 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:281040 (274.4 KiB) TX bytes:26056 (25.4 KiB)
eth1 Link encap:Ethernet HWaddr 00:0C:29:64:C4:8A
inet addr:192.216.6.78 Bcast:192.216.6.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe64:c48a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1201 errors:0 dropped:0 overruns:0 frame:0
TX packets:421 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:80721 (78.8 KiB) TX bytes:93549 (91.3 KiB)
Base address:0x1078 Memory:f4840000-f4860000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1664 errors:0 dropped:0 overruns:0 frame:0
TX packets:1664 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2460982 (2.3 MiB) TX bytes:2460982 (2.3 MiB)
peth0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:6152 errors:0 dropped:0 overruns:0 frame:0
TX packets:376 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:384572 (375.5 KiB) TX bytes:44157 (43.1 KiB)
Base address:0x1070 Memory:f4820000-f4840000
vif0.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:332 errors:0 dropped:0 overruns:0 frame:0
TX packets:5989 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:36048 (35.2 KiB) TX bytes:372384 (363.6 KiB)
virbr0 Link encap:Ethernet HWaddr 00:00:00:00:00:00
inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0
inet6 addr: fe80::200:ff:fe00:0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:53 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:10188 (9.9 KiB)
xenbr0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF
UP BROADCAST RUNNING NOARP MTU:1500 Metric:1
RX packets:6158 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:311095 (303.8 KiB) TX bytes:0 (0.0 b)
解决办法：怀疑这些多余的配置冲突导致了该服务无法连接网络，尝试删除virbr0、xenbr0等多余的信息，即vi /boot/grub/grub.conf把其中的default=0改为default=1后，保存退出，reboot服务器即可解决问题。
再使用ifconfig查看到的信息如下：
[root@EXFO ~]# ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:64:C4:80
inet addr:XXX.XX.XX.XX Bcast:XXX.XX.XX.XX Mask:255.255.255.192
inet6 addr: fe80::20c:29ff:fe64:c480/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1172206 errors:0 dropped:0 overruns:0 frame:0
TX packets:75628 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:93410582 (89.0 MiB) TX bytes:28185193 (26.8 MiB)
Base address:0x1070 Memory:f4820000-f4840000
eth1 Link encap:Ethernet HWaddr 00:0C:29:64:C4:8A
inet addr:192.216.6.78 Bcast:192.216.6.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe64:c48a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5172160 errors:0 dropped:0 overruns:0 frame:0
TX packets:2407634 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:4108624765 (3.8 GiB) TX bytes:139136852 (132.6 MiB)
Base address:0x1078 Memory:f4840000-f4860000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:1182 errors:0 dropped:0 overruns:0 frame:0
TX packets:1182 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1823252 (1.7 MiB) TX bytes:1823252 (1.7 MiB)
[root@EXFO ~]#
virbr0、xenbr0等多余的信息已消失，此服务器可上网。