# 網路指令與技巧 #### Tutorials - [Linux See Bandwidth Usage Per Process With Nethogs Tool](https://www.cyberciti.biz/faq/linux-find-out-what-process-is-using-bandwidth/) - [How to Configure Network Interfaces in Linux](https://www.freecodecamp.org/news/configure-network-interfaces-in-linux/) #### ip ```shell # 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 -br -c 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 # 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 ```shell # 1. 列出所有網路埠 ip link show 如果埠號顯示 DOWN 必須先啟動 # 2. 啟動網路埠 NOTE: 啟動前要注意 IP 是否會衝突 ip link set eth6 up # 3. 啟動後檢測線路 ethtool eth6 | grep detected ``` Cheat Sheet [![ip_commnad.jpeg](https://osslab.tw/uploads/images/gallery/2023-08/scaled-1680-/ip-commnad.jpeg)](https://osslab.tw/uploads/images/gallery/2023-08/ip-commnad.jpeg) #### nmcli ```shell # List all of ethernet devices nmcli con show nmcli con show 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 # The settings persist across reboots because they are stored by NetworkManager 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 ```bash # For Ubuntu/Debian sudo apt install network-manager # Console Command nmtui ``` #### netplan Recommended on Ubuntu/Debian - [A declarative approach to Linux networking with Netplan | Ubuntu](https://ubuntu.com/blog/a-declarative-approach-to-linux-networking-with-netplan) - [Netplan brings consistent network configuration across Desktop, Server, Cloud and IoT | Ubuntu](https://ubuntu.com//blog/netplan-configuration-across-desktop-server-cloud-and-iot) `sudo vi /etc/netplan/01-network-manager-all.yaml` ``` network: version: 2 renderer: networkd ethernets: ens18: dhcp4: no addresses: - 192.168.1.22/24 gateway4: 192.168.1.101 nameservers: addresses: [8.8.8.8, 8.8.4.4] ``` Commands ```bash # Validate Configuration File sudo netplan try # Apply the Configuration sudo netplan apply # Check the network stack sudo netplan status # Optional: Restart the Network Service sudo systemctl restart systemd-networkd ``` #### ethtool ``` # ethtool ens192 Settings for ens192: Supported ports: [ TP ] Supported link modes: 1000baseT/Full 10000baseT/Full Supported pause frame use: No Supports auto-negotiation: No Supported FEC modes: Not reported Advertised link modes: Not reported Advertised pause frame use: No Advertised auto-negotiation: No Advertised FEC modes: Not reported Speed: 10000Mb/s Duplex: Full Port: Twisted Pair PHYAD: 0 Transceiver: internal Auto-negotiation: off MDI-X: Unknown Supports Wake-on: uag Wake-on: d Link detected: yes ``` ``` # ethtool -i ens192 driver: vmxnet3 version: 1.4.17.0-k-NAPI firmware-version: expansion-rom-version: bus-info: 0000:0b:00.0 supports-statistics: yes supports-test: no supports-eeprom-access: no supports-register-dump: yes supports-priv-flags: no ``` ``` # ethtool -S ens192 NIC statistics: Tx Queue#: 0 TSO pkts tx: 540499 TSO bytes tx: 28911908774 ucast pkts tx: 10060867 ucast bytes tx: 29602317140 mcast pkts tx: 0 mcast bytes tx: 0 bcast pkts tx: 5655 bcast bytes tx: 237510 pkts tx err: 0 pkts tx discard: 0 drv dropped tx total: 0 too many frags: 0 giant hdr: 0 hdr err: 0 tso: 0 ring full: 0 pkts linearized: 0 hdr cloned: 0 giant hdr: 0 Tx Queue#: 1 TSO pkts tx: 317 TSO bytes tx: 599134 ucast pkts tx: 1702836 ucast bytes tx: 101410145 ``` #### mii-tool ```shell # Installation sudo apt install net-tools # CHECK A SINGLE INTERFACE sudo mii-tool # SEE DETAILED INFORMATION sudo mii-tool -v # SET NETWORK INTERFACE SPEED sudo mii-tool –force 10baseT-FD # 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 # 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 # REPORT LINK STATUS sudo mii-tool -l # 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 ``` #### systemctl ``` # Bringing UP/Down Network Interface systemctl restart network # or systemctl restart network.service ``` #### speedtest CLI ```shell # Ubuntu/Debian curl -s https://packagecloud.io/install/repositories/ookla/speedtest-cli/script.deb.sh | sudo bash sudo apt-get install speedtest # CentOS/RedHat curl -s https://packagecloud.io/install/repositories/ookla/speedtest-cli/script.rpm.sh | sudo bash sudo yum install speedtest ``` #### State of Network Cable ```shell # Device: enp5s0 # Output: 1 means Connected cat /sys/class/net/enp5s0/carrier # Output: Up means Connected cat /sys/class/net/enp5s0/operstate # Using ethtool # Output: Link detected: yes sudo ethtool enp5s0 # Using ip # Output: state UP ip a ``` #### Network Adapters Modern Linux ```bash lshw -class network -short ``` Old Linux ```bash lspci | egrep -i --color 'network|ethernet' ``` #### Disable IPv6 - [Disable IPv6 in Linux: A Step-by-Step Guide (For All Distros) - OSTechNix](https://ostechnix.com/disable-ipv6-in-linux/) ##### Ubuntu 20.04 ``` sudo vi /etc/default/grub # Change the line as follows GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1" # Update the GRUB sudo update-grub # Reboot systemctl reboot ``` ##### Debian 10/11/12 `/etc/sysctl.d/ipv6.conf` : ```shell # Disable IPv6 on all network adapters net.ipv6.conf.all.disable_ipv6 = 1 ``` Apply the change : ```shell # Debian 12+ service procps force-reload # Older systems sysctl -p ``` ##### RedHat 4 1\. Remove the following line (if present) from the `/etc/modprobe.conf` file: ``` alias net-pf-10 ipv6 ``` 2\. Add the following line to the `/etc/modprobe.conf` file: ``` alias net-pf-10 off ``` 3\. Comment out any IPv6 addresses found in `/etc/hosts`, including ::1 localhost address ``` cp -p /etc/hosts /etc/hosts.disableipv6 sed -i 's/^[[:space:]]*::/#::/' /etc/hosts ``` 如果以上步驟仍無法關閉 IPv6，檢查是否有啟動 openibd 服務，將它關閉試試 > **openibd** is a High Availability service for IPoIB (IP over InfiniBand) interface. The service loads the ib\_ipoib module, which has a dependency on the ipv6 module ```bash service openibd stop chkconfig openibd off reboot ``` ##### RedHat 5/6 `/etc/sysctl.d/ipv6.conf` : ``` # For v5/6 # IPv6 support in the kernel, set to 0 by default # Disable IPv6 net.ipv6.conf.all.disable_ipv6 = 1 net.ipv6.conf.default.disable_ipv6 = 1 ``` ##### RedHat 7 `/etc/sysctl.d/ipv6.conf` : ``` # To disable for all interfaces net.ipv6.conf.all.disable_ipv6 = 1 ``` 重建開機映像檔 > 如果沒有重建開機映像檔，會使得 rpcbind.service 無法正常運作，這會影響 NFS 的掛載。 ##### RedHat 8 Create the file `/etc/sysctl.d/ipv6.conf` : ``` # First, disable for all interfaces net.ipv6.conf.all.disable_ipv6 = 1 # If using the sysctl method, the protocol must be disabled all specific interfaces as well. #net.ipv6.conf..disable_ipv6 = 1 ``` Reload sysctl : ``` sysctl -p /etc/sysctl.d/ipv6.conf ``` Create a backup of the initramfs : ``` cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).bak.$(date +%m-%d-%H%M%S).img ``` Rebuild the Initial RAM Disk Image : ``` dracut -f -v ``` Verifying file inclusion : ``` lsinitrd /boot/initramfs-.img | grep 'etc/sysctl.d/ipv6.conf' ``` Comment out any IPv6 addresses found in /etc/hosts, including ::1 localhost address ``` cp -p /etc/hosts /etc/hosts.disableipv6 sed -i 's/^[[:space:]]*::/#::/' /etc/hosts ``` #### WiFi Management - [8 Linux Commands: To Find Out Wireless Network Speed, Signal Strength And Other Information](https://www.cyberciti.biz/tips/linux-find-out-wireless-network-speed-signal-strength.html) ```shell // Show All SSIDs nmcli dev wifi // Get dev name nmcli conn show # Replace 'wlan0' with your wifi interface sudo iwlist wlan0 scan | egrep "Cell|ESSID|Encryption|Quality" ``` #### Block Attackers IP Address Drop or Block Attackers IP Address With Null Routes On a Linux ```shell # Using route command route add 65.21.34.4 gw 127.0.0.1 lo # veryfy it netstat -nr route -n # Or route add -host 64.1.2.3 reject ip route get 64.1.2.3 # Using ip command ip route add blackhole 202.54.5.2/29 ip route add blackhole 192.0.130.0/24 # verify it ip route # Removing null routing route delete 65.21.34.4 # Or route del -host 65.21.34.4 reject # Or ip route delete 1.2.3.4/26 dev eth0 ``` #### 重設/移除不存在的網路裝置名稱 製作 Linux VM Template 時，每一次修改 Template 後都會產生新的編號作為網路裝置名稱。 然而透過這個 Template 新增的 Linux VM，系統的網路介面其實只有一個，不過裝置名稱可能已經編到 eth1 或 eth2 以後。正常來說，系統如果只有一個網路介面，網路裝置名稱通常為 eth0。 假使想要清除那些已經不存在的裝置名稱，或者讓系統對目前的網路裝置重新以 eth0 開始編號，步驟如下： RedHat 6.x: 編輯 /etc/udev/rules.d/70-persistent-net.rules ``` # PCI device 0x15ad:0x07b0 (vmxnet3) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:83:7c:eb", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0" # PCI device 0x15ad:0x07b0 (vmxnet3) (custom name provided by external tool) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:83:7c:eb", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1" ``` 註解或移除那些舊裝置名稱，只保留目前的裝置 eth1，然後將該行的 NAME 改成 eth0。 ``` # PCI device 0x15ad:0x07b0 (vmxnet3) (custom name provided by external tool) SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:50:56:83:7c:eb", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0" ``` 存檔後重起 VM。 VM 啟動後，使用 `setup` 或 system-config-network 新增網路介面 eth0 的網路設定。 #### Disable WiFi With nmcli ``` # nmcli dev status DEVICE TYPE STATE CONNECTION enp2s0 ethernet 已連線 enp2s0 wlp1s0 wifi 離線 -- lo loopback 不受管理 -- # nmcli radio wifi off # nmcli dev status DEVICE TYPE STATE CONNECTION enp2s0 ethernet 已連線 enp2s0 wlp1s0 wifi 無法使用 -- lo loopback 不受管理 -- ``` #### 查詢 DNS Server 位址 ```bash cat /etc/resolv.conf nmcli dev show | grep -i dns dig resolvectl status ``` #### Custom MAC Address ##### RedHat 4 `/etc/sysconfig/network-scripts/ifcfg-eth0` ``` DEVICE=eth0 ONBOOT=yes BOOTPROTO=static IPADDR=10.15.9.32 NETMASK=255.255.0.0 GATEWAY=10.15.8.254 #HWADDR=00:0C:29:B1:18:A3 MACADDR=00:0C:B1:B1:B1:B1 ```