網路管理

ip
# 顯示所有網卡資訊
ip addr
ip a

# 顯示所有網卡的 IP
ip -br -c addr show  # 需要較新版 ip

# 顯示 eth0 網卡資訊
ip a show eth0 

# 開啟/關閉網卡
ip link set eth0 { up | down }

# 顯示所有的網路裝置
ip link show
ip l show

# 設定 IP (非永久)
ip a add 192.168.1.200/255.255.255.0 dev eth0

# 移除 IP (非永久)
ip a del 192.168.1.200/255.255.255.0 dev eth0

# 顯示 default gateway 及路由表
ip route show
ip r show
ip route add 10.10.20.0/24 via 192.168.50.100 dev eth0
ip route del 10.10.20.0/24

# Default gateway
ip route add default via 192.168.50.100

# 網路即時狀態
ip -s link 

# 顯示 ARP 紀錄 (NOTE: 查詢連接網路設備的 MAC address 與 IP 對應表)
ip neigh show
ip n show

# 清除 ARP 清單裡的某個 IP 紀錄
ip -s -s n f <ip-address>

# 線上求助
ip a help

在多個網路埠的主機上,如何得知哪些埠有接上網路線

nmcli
# List all of ethernet devices
nmcli con show
nmcli con show <conn-name>
nmcli dev status
# see only the active connections
nmcli con show -a

# Restart the network adapter enp0s3
nmcli con down enp0s3 && nmcli con up enp0s3

# Configure the static ip
nmcli con mod enp0s3 ipv4.addresses 192.168.20.170/24
nmcli con mod enp0s3 ipv4.gateway 192.168.20.1
nmcli con mod enp0s3 ipv4.method manual
nmcli con mod enp0s3 ipv4.dns "8.8.8.8"

nmcli con down enp0s3
nmcli con up enp0s3 

# make a new ethernet connection with name Myhome1, assigned to device enp0s3
nmcli con add type ethernet con-name Myhome1 ifname enp0s3 ip4 192.168.1.50/24 gw4 192.168.1.1
cat /etc/sysconfig/network-scripts/ifcfg-Myhome1
GUI to Configure Network
nmtui
nc - netcat
# Scanning the port range (20 - 1024)
nc -z 192.168.21.202 20-1024

Connection to 192.168.21.202 22 port [tcp/ssh] succeeded!
Connection to 192.168.21.202 80 port [tcp/http] succeeded!
Connection to 192.168.21.202 111 port [tcp/sunrpc] succeeded!
Connection to 192.168.21.202 443 port [tcp/https] succeeded!
Connection to 192.168.21.202 514 port [tcp/shell] succeeded!

# Scanning the specified port
nc -zv 192.168.21.202 21
nc: connect to 192.168.21.202 port 21 (tcp) failed: Connection refused

# Port Scanning With netcat including displaying version #
echo "QUIT" | nc 192.168.2.17 22
echo "QUIT" | nc -v 192.168.2.254 ssh
# OR pass the -vv  to get remote OpenSSH version # 
nc -vv 192.168.2.254 ssh
mii-tool
# Installation 
sudo apt install net-tools

# CHECK A SINGLE INTERFACE
sudo mii-tool <interface_name>

# SEE DETAILED INFORMATION
sudo mii-tool -v <interface_name>

# SET NETWORK INTERFACE SPEED
sudo mii-tool –force 10baseT-FD <interface_name>

# RESTART AUTO-NEGOTIATION
# Network devices use an auto-negotiation protocol to communicate the technologies they support. 
# It will then select the fastest mutually supported technology. 
# To restart the auto-negotiation of the interface, run the following command.
sudo mii-tool –restart <interface_name>

# CHANGE THE DUPLEX MODE
# For example, here I have set the speed of the eth0 interface to 10 Mbps and the duplex mode to half-duplex.
sudo mii-tool -F 10baseT-HD eth0

# REPORT LINK STATUS CHANGES
# Run the following command to watch a single interface and report changes in the link status. 
# That is to say, the interfaces are listed at one second intervals by default.
sudo mii-tool -w <interface>

# REPORT LINK STATUS
sudo mii-tool -l <interface_name>

# RESET THE CONFIGURATIONS
# Most importantly, you should be able to reset it to its default configuration 
# if something goes wrong. For that, run the following command
sudo mii-tool -R <Interface_name>