Linux Basic network Settings

# # # One, Linux basic network settings
# # # 1, view and test the network

##### 1) View network configuration
-**ifconfig Command * *
```
Ifconfig//view Active network interface information

```
* * Network Card Knowledge Introduction: * *

Eth0, lo: network interface name

HWADDR: Network card MAC Address

inet addr: IP address of the network interface

Bcast: The broadcast address of the network where the network interface resides

Mask: Subnet mask for network interface


```
[Email protected] ~]# ifconfig
Eth0 Link encap:ethernet HWaddr 00:0c:29:b2:44:8f
inet addr:192.168.1.125 bcast:192.168.1.255 mask:255.255.255.0
Inet6 ADDR:FE80::20C:29FF:FEB2:448F/64 Scope:link
Up broadcast RUNNING multicast mtu:1500 metric:1
RX packets:132226 errors:0 dropped:0 overruns:0 frame:0
TX packets:23844 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:12420847 (11.8 MiB) TX bytes:14671857 (13.9 MiB)

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:2 errors:0 dropped:0 overruns:0 frame:0
TX packets:2 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:104 (104.0 b) TX bytes:104 (104.0 b)


```




To view the interface information for all network cards:

Ifconfig-a

To view the interface information for a piece of Nic:

Ifconfig eth0
-**ip/ethtool Command * *

```
IP link//View data link layer information for all network interfaces
IP link Show eth0//View Data link layer information for a specified NIC

```
```
IP address//view network layer information for all network interfaces
IP address show eth0//view network layer information for the specified network card
```
```
Ethtool eth0//View physical attribute information such as rate, mode, etc. for a specified network interface
```

```
[[Email protected] ~]# IP link
1:lo: <LOOPBACK,UP,LOWER_UP> MTU 16436 qdisc noqueue State UNKNOWN
Link/loopback 00:00:00:00:00:00 BRD 00:00:00:00:00:00
2:eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> MTU Qdisc pfifo_fast State up Qlen 1000
Link/ether 00:0c:29:b2:44:8f BRD FF:FF:FF:FF:FF:FF
[[Email protected] ~]# IP addr
1:lo: <LOOPBACK,UP,LOWER_UP> MTU 16436 qdisc noqueue State UNKNOWN
Link/loopback 00:00:00:00:00:00 BRD 00:00:00:00:00:00
inet 127.0.0.1/8 Scope host Lo
INET6:: 1/128 Scope Host
Valid_lft Forever Preferred_lft Forever
2:eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> MTU Qdisc pfifo_fast State up Qlen 1000
Link/ether 00:0c:29:b2:44:8f BRD FF:FF:FF:FF:FF:FF
inet 192.168.1.125/24 BRD 192.168.1.255 Scope Global eth0
Inet6 FE80::20C:29FF:FEB2:448F/64 Scope link
Valid_lft Forever Preferred_lft Forever
```
-**hostname/route Command * *

```
[[email protected] ~]# hostname//View host name
Test2
```
```
[[email protected] ~]# route//View routing table
Kernel IP Routing Table
Destination Gateway genmask Flags Metric Ref use Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
link-local * 255.255.0.0 U 1002 0 0 eth0
Default localhost 0.0.0.0 UG 0 0 0 eth0
[[email protected] ~]# route-n//View routing table, all with IP address display
Kernel IP Routing Table
Destination Gateway genmask Flags Metric Ref use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 eth0
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
```
-**netstat Command * *

viewing Network Connections = = (e.g. port monitoring) = =

Options | Role
---|---
-A | Displays network connection information for all activities in the current host
-N | Display related information in digital form
-r | Show routing table information
-T | Displaying TCP protocol-related information
-u | displaying UDP protocol-related information
-L | Display the service information in the listening
-P | Displays the process number, process name information associated with the network connection (requires root permission)

Typically use the "-ANPT", "UTPLN" combination options


```
[[email protected] ~]# NETSTAT-ANPT |grep SSH
TCP 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 2122/sshd
TCP 0 192.168.1.125:22 192.168.1.109:50992 established 47349/sshd
TCP 0 0::: $:::* LISTEN 2122/sshd
[[email protected] ~]# NETSTAT-UTPLN |grep SSH
TCP 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 2122/sshd
TCP 0 0::: $:::* LISTEN 2122/sshd
```


##### 2) test network connection

-**ping/traceroute/nslookup Command * *

```
Ping//test network connectivity
-c//Specify the number of packets
```
```
Traceroute//routing path for tracking packets
```

```
[Email protected] ~]# traceroute 192.168.1.101
Traceroute to 192.168.1.101 (192.168.1.101), hops max, byte packets
1 localhost (192.168.1.125) 3006.931 MS! H 3006.930 MS! H 3006.927 MS! H

```

```
Nslookup//Testing DNS domain name resolution
```

```
[[email protected] ~]# nslookup www.baidu.com//Resolve a domain name directly
server:202.106.195.68//Resolved server
ADDRESS:202.106.195.68#53//parsing the port of the service

Non-authoritative Answer:
www.baidu.com canonical name = www.a.shifen.com.
Name:www.a.shifen.com
address:61.135.169.121
Name:www.a.shifen.com
address:61.135.169.125

[[email protected] ~]# nslookup www.baidu.com 8.8.8.8//You can also specify a server to parse
server:8.8.8.8
address:8.8.8.8#53

Non-authoritative Answer:
www.baidu.com canonical name = www.a.shifen.com.
Name:www.a.shifen.com
address:61.135.169.121
Name:www.a.shifen.com
address:61.135.169.125

```




# # 2, set network address parameters

##### 1) Using the Network configuration command

In a Linux environment, there are two basic ways to manually modify a network configuration:

-Temporary configuration:

Direct modification through the command, the modification can take effect immediately, generally used to debug the network, restart the service or host will be invalid;

```
Ifconfig eth0 192.168.1.10 netmask 255.255.255.0 Gateway 192.168.1.1
```

```
Ifconfig eth0 up//enable Eth0 network interface
Ifconfig eth0 down//disable Eth0 network interface
```

```
IFCONIFG eth0:0 10.10.10.10//Bind virtual interface for NIC
```


-Fixed configuration:

By modifying the parameters in the configuration file, the service needs to be restarted before it takes effect; "Permanent configuration"

```
Vi/etc/sysconfig/network-scripts/ifcfg-eth0
```

To modify the host name using the hostname command:


```
Hostname deeption//Temporary settings
```

To add and remove static routes using the route command:

-Specify the route for the network segment:

```
Route add-net 192.168.2.0/24 GW x.x.x.x//Add
Route del-net 192.168.2.0/24//delete
```

-Default route (Gateway):

```
Route add default GW x.x.x.x//Add
Route del default GW x.x.x.x//delete
Route | grep default//view defaults route
```


##### 2) Modify the network configuration file

The configuration file of the network interface is located by default in the directory "/etc/sysconfig/network-scripts/", the file name format is "Ifcfg-xxx", where "XXX" is the name of the network interface, such as Eth0, lo

-Permanently set the network interface configuration:
```
Vi/etc/sysconfig/network-scripts/ifcfg-eth0
```

```
Network interface configuration file contents:
Device=eth0//network Interface Device name
Type=ethernet
uuid=adf9d271-d77d-4b4c-a4fd-58eb0c85d663
Onboot=yes//Set Boot active
Nm_controlled=no//General set to No, indicates that the System Network management tool does not control this NIC
Bootproto=static//Set static IP address or DHCP
Defroute=yes
Ipv4_failure_fatal=yes
Ipv6init=no
Name= "System eth0"
hwaddr=00:0c:29:b2:44:8f
last_connect=1462590913
IPADDR=192.168.1.125//Set IP address
netmask=255.255.255.0//Set subnet mask
gateway=192.168.1.1//Set default gateway
```
-Command to restart the network service:

```
Service network restart//will restart all networking interfaces
```
-Restart a network interface command:

```
Ifdown eth0
Ifup eth0
```
Note: The temporarily configured subinterface disappears after the NIC restarts

-Permanently set host name:

```
Vi/etc/sysconfig/network
```

```
Hostname Configuration file Contents:
Networking=yes
Hostname=test2

```
-Permanently set the domain name resolution server:
```
Vi/etc/resolv.conf
```
```
Domain name resolution configuration file contents:
NameServer 202.106.195.68//dns Server, parsing sequence is used from top to bottom
NameServer 202.106.46.151
```
-Local Host mapping File (hosts):

The >/etc/hosts file records a mapping relationship table of hostname and IP address, which is commonly used to store host information that is often needed for access.

> When accessing an unknown domain name, first find the Hosts file, if not to ask the DNS server.

```
[Email protected] ~]# cat/etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.local
:: 1 localhost localhost.localdomain localhost6 localhost6.loca
Alias name alias for IP address domain name
```

The above is the simplest network knowledge ╮ (￣▽￣) ╭



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Linux Basic network Settings