Linux network configuration

Temporary Change Solution：

#ifconfig eth0 192.168.0.1 netmask 255.255.255.0 up

Permanent Change Solution：

Step1 Change config file：/etc/sysconfig/network-scripts/ifcfg-eth0

(Or use system-config-network command to config but remember to check config file)

dynamic IP config：

DEVICE=eth0
BOOTPROTO=dhcp
HWADDR=00:03:47:2C:D5:40
ONBOOT=yes
TYPE=Ethernet

static IP config：

DEVICE=eth0
BOOTPROTO=static
IPADDR=192.168.1.223

NETMASK=255.255.255.0
GATEWAY=192.168.1.1

HWADDR=00:03:47:2C:D5:40
ONBOOT=yes
TYPE=Ethernet

Step2. restart service：

Before Linux 6.0:

service network restart

 

Linux 6.0: 

service NetworkManager restart

service network restart

 

Addintional

network --> /etc/rc.d/init.d/network

NetworkManager --> /etc/rc.d/init.d/NetworkManager

 

Check network adapter status: mii_tool / ip link

Close the feedback of ping: echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

Check network connection: ping / traceroute <domain name> / mtr <domain name> / dig / host / iptraf

Load check: ab -n 1000 -c 1000 <domain name>

Example: ab -n 1000 -c 1000 www.sina.com.cn

Check the firewall setting: iptables -L

Temporary clear the firewall setting: iptables -F

Check network status: netstat -antup

Attention: 

netstat -antup | wc -l is huge

1. If there are a lot of "Established" connections and the source IP address is same, the server got the CC network attack;

2. If the status of "Established" is little, it may receive the DDOS or syn_flood attack;

Check about arp attack:

1. check arping <gateway ip>

If the feedback is the same MAC address, there is no arp attack. Otherwise there is arp attack.

Solution: setup the right gateway: arp -s <gateway ip address> <gateway mac address>

Error: mac address different

Solution: check the mac address in Virtual Box setting of the vm server

Setup several ipaddress

Temporary

ifconfig eth0:0 12.11.0.136/24

ifconfig eth0:1 12.11.0.137/24

ifconfig eth0:2 12.11.0.138/24

Permanent

vim /etc/sysconfig/network-scripts/ifcfg-eth0:0

DEVICE=eth0:0

onboot=yes

BOOTPORTO=static

IPADDR=12.11.0.136

NETMASK=255.255.255.0

GATEWAY=12.11.0.100

vim /etc/sysconfig/network-scripts/ifcfg-eth0:1

DEVICE=eth0:1

onboot=yes

BOOTPORTO=static

IPADDR=12.11.0.137

NETMASK=255.255.255.0

GATEWAY=12.11.0.100

vim /etc/sysconfig/network-scripts/ifcfg-eth0:2

DEVICE=eth0:2

onboot=yes

BOOTPORTO=static

IPADDR=12.11.0.138

NETMASK=255.255.255.0

GATEWAY=12.11.0.100

After clone virtual box system, the mac address will not change.

1. change the system config file /etc/udev/rules.d/70-persistent-net.rules

The new mac will be used as eth1, the original one will be used as eth0

Remove the eth0 config and change eth1 as eth0

2. change the network adaptor config file /etc/sysconfig/network-scripts/ifcfg-eth0

use new mac instead of old one. 

3. restart network service: service network restart