维护系统和网络安全运行是系统/网络管理员的主要工作。下面是华纳云分享的linux系统中常用的网络配置和故障排除命令。

ifconfig是接口配置器命令可以用于初始化接口、给接口分配IP地址及根据需要启用或禁用接口。查看分配给接口的IP地址或硬件/MAC地址及MTU大小：

# ifconfig

eth0      Link encap:Ethernet  HWaddr 00:0C:29:28:FD:4C

inet addr:192.168.50.2  Bcast:192.168.50.255  Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe28:fd4c/64 Scope:Link

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

RX packets:6093 errors:0 dropped:0 overruns:0 frame:0

TX packets:4824 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:6125302 (5.8 MiB)  TX bytes:536966 (524.3 KiB)

Interrupt:18 Base address:0x2000

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:8 errors:0 dropped:0 overruns:0 frame:0

TX packets:8 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:0

RX bytes:480 (480.0 b)  TX bytes:480 (480.0 b)

把带接口命令的Ifconfig之显示特定接口详细信息，如IP地址\MAC地址等。如果禁用a则会显示全部可用的接口详细信息：

# ifconfig eth0

eth0      Link encap:Ethernet  HWaddr 00:0C:29:28:FD:4C

inet addr:192.168.50.2  Bcast:192.168.50.255  Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe28:fd4c/64 Scope:Link

UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

RX packets:6119 errors:0 dropped:0 overruns:0 frame:0

TX packets:4841 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:6127464 (5.8 MiB)  TX bytes:539648 (527.0 KiB)

Interrupt:18 Base address:0x2000

在linux中动态为接口分配IP地址和网关，系统重启后会删除这个设置。

# ifconfig eth0 192.168.50.5 netmask 255.255.255.0

启用eth0:

# ifup eth0

禁用eth0:

# ifdown eth0

设置MTU大小，通常MTU大小为1500，替换成所需大小：

# ifconfig eth0 mtu XXXX

把接口设置为混杂模式。网络接口只接收属于特定NIC数据包，如果把接口置于混杂模式，可以接收全部数据包，对于捕获数据包并在以后分析非常有效，前提是有超级用户访问权限：

# ifconfig eth0-promisc

大部分linux发行版中ifconfig被IP命令取代。

不管是局域网还是广域网Ping命令是测试两个节点之间连通性的有效方法。Ping还可以用ICMP和其他设备通信。用下面命令ping主机名或者IP地址。

# ping 4.2.2.2

PING 4.2.2.2 (4.2.2.2) 56(84) bytes of data.

64 bytes from 4.2.2.2: icmp_seq=1 ttl=44 time=203 ms

64 bytes from 4.2.2.2: icmp_seq=2 ttl=44 time=201 ms

64 bytes from 4.2.2.2: icmp_seq=3 ttl=44 time=201 ms

OR

# ping www.tecmint.com

PING tecmint.com (50.116.66.136) 56(84) bytes of data.

64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=284 ms

64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=287 ms

64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms

Linux中,ping命令会持续执行知道终端，N次请求后用exit执行ping :

# ping -c 5 www.tecmint.com

PING tecmint.com (50.116.66.136) 56(84) bytes of data.

64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=285 ms

64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=285 ms

64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms

64 bytes from 50.116.66.136: icmp_seq=4 ttl=47 time=285 ms

64 bytes from 50.116.66.136: icmp_seq=5 ttl=47 time=285 ms

--- tecmint.com ping statistics ---

5 packets transmitted, 5 received, 0% packet loss, time 4295ms

rtt min/avg/max/mdev = 285.062/285.324/285.406/0.599 ms

Traceroute属于网络故障排除实用程序，可以显示到达目的地需要多少跳数，还确定数据包的传输路径。跟踪全局DNS服务器IP地址路由，到达目的地显示数据包传输路由：

# traceroute 4.2.2.2

traceroute to 4.2.2.2 (4.2.2.2), 30 hops max, 60 byte packets

1  192.168.50.1 (192.168.50.1)  0.217 ms  0.624 ms  0.133 ms

2  227.18.106.27.mysipl.com (27.106.18.227)  2.343 ms  1.910 ms  1.799 ms

3  221-231-119-111.mysipl.com (111.119.231.221)  4.334 ms  4.001 ms  5.619 ms

4  10.0.0.5 (10.0.0.5)  5.386 ms  6.490 ms  6.224 ms

5  gi0-0-0.dgw1.bom2.pacific.net.in (203.123.129.25)  7.798 ms  7.614 ms  7.378 ms

6  115.113.165.49.static-mumbai.vsnl.net.in (115.113.165.49)  10.852 ms  5.389 ms  4.322 ms

7  ix-0-100.tcore1.MLV-Mumbai.as6453.net (180.87.38.5)  5.836 ms  5.590 ms  5.503 ms

8  if-9-5.tcore1.WYN-Marseille.as6453.net (80.231.217.17)  216.909 ms  198.864 ms  201.737 ms

9  if-2-2.tcore2.WYN-Marseille.as6453.net (80.231.217.2)  203.305 ms  203.141 ms  202.888 ms

10  if-5-2.tcore1.WV6-Madrid.as6453.net (80.231.200.6)  200.552 ms  202.463 ms  202.222 ms

11  if-8-2.tcore2.SV8-Highbridge.as6453.net (80.231.91.26)  205.446 ms  215.885 ms  202.867 ms

12  if-2-2.tcore1.SV8-Highbridge.as6453.net (80.231.139.2)  202.675 ms  201.540 ms  203.972 ms

13  if-6-2.tcore1.NJY-Newark.as6453.net (80.231.138.18)  203.732 ms  203.496 ms  202.951 ms

14  if-2-2.tcore2.NJY-Newark.as6453.net (66.198.70.2)  203.858 ms  203.373 ms  203.208 ms

15  66.198.111.26 (66.198.111.26)  201.093 ms 63.243.128.25 (63.243.128.25)  206.597 ms 66.198.111.26 (66.198.111.26)  204.178 ms

16  ae9.edge1.NewYork.Level3.net (4.68.62.185)  205.960 ms  205.740 ms  205.487 ms

17  vlan51.ebr1.NewYork2.Level3.net (4.69.138.222)  203.867 ms vlan52.ebr2.NewYork2.Level3.net (4.69.138.254)  202.850 ms vlan51.ebr1.NewYork2.Level3.net (4.69.138.222)  202.351 ms

18  ae-6-6.ebr2.NewYork1.Level3.net (4.69.141.21)  201.771 ms  201.185 ms  201.120 ms

19  ae-81-81.csw3.NewYork1.Level3.net (4.69.134.74)  202.407 ms  201.479 ms ae-92-92.csw4.NewYork1.Level3.net (4.69.148.46)  208.145 ms

20  ae-2-70.edge2.NewYork1.Level3.net (4.69.155.80)  200.572 ms ae-4-90.edge2.NewYork1.Level3.net (4.69.155.208)  200.402 ms ae-1-60.edge2.NewYork1.Level3.net (4.69.155.16)  203.573 ms

21  b.resolvers.Level3.net (4.2.2.2)  199.725 ms  199.190 ms  202.488 ms