What is promiscuous mode in linux

Настройка интерфейса в режиме «Promiscuous Mode» в CentOS

Режим Promiscuous или режим promisc — это функция, которая заставляет карту ethernet передавать весь полученный трафик ядру. Обычно она используется программами для перехвата пакетов, такими как Wireshark и tcpdump.

Когда сетевая карта находится в режиме promiscuous, она может читать весь полученный трафик, а не только адресованные ей пакеты. Предположим, что для eth1 режим promiscuous используется для передачи всего трафика, который получает ‘eth1’, а не только адресованных ему кадров. Сетевая карта обычно находится в режиме promiscuous, когда:

• Если она была вручную настроена в этот режим с помощью команды ifconfig.
• Если используется инструмент сетевого монитора, например tcpdump и т.д.
• При использовании моста сетевая карта в основном должна работать в режиме promiscuous.

Вручную установить сетевую карту в режим Promiscuous Mode

Чтобы перевести интерфейс в режим promiscuous, можно использовать любую из этих команд, но наиболее актуальным способом является использование команды ‘ip’.

ifconfig [interface] promisc

ip link set [interface] promisc on

Постоянные настройки Promiscuous Mode

Чтобы перевести интерфейс в постоянный режим promiscuous, необходимо в конец файла ifcfg-ethX добавить «PROMISC=yes»

nano /etc/sysconfig/network-scripts/ifcfg-eth1

Источник

How to configure interface in “Promiscuous Mode” in CentOS/RHEL

Promiscuous mode or promisc mode is a feature that makes the ethernet card pass all traffic it received to the kernel. It is usually used by a packet sniffing program like Wireshark, and tcpdump. If there was such program intentionally running or bridged networking for hardware virtualization, the “promiscuous mode” message might be simply ignored. Otherwise, deep investigation on that system will be required due to a security issue.

When a network card is in promiscuous mode, it can read all traffic it received rather than just packages addressed to it. Suppose for eth1, promiscuous mode is basically used to pass all traffic that ‘eth1’ receives rather than just frames addressed to it. A network card usually is in promiscuous mode when:

1. If it was manually configured in that mode using ifconfig command.
2. If a Network monitor tool is used, like tcpdump etc.
3. In bridge network, the NIC is mostly required to operate in promiscuous mode.

How to Manually set a NIC in Promiscuous Mode?

To set an interface to promiscuous mode you can use either of these commands, using the ‘ip’ command is the most current way.

# ifconfig [interface] promisc

# ip link set [interface] promisc on

To identify if the NIC has been set in Promiscuous Mode, use the ifconfig command.

# ifconfig eth1 eth1 Link encap:Ethernet HWaddr 08:00:27:CD:20:16 inet addr:192.168.200.56 Bcast:192.168.255.255 Mask:255.255.0.0 inet6 addr: 2606:b400:c10:6044:a00:27ff:fecd:2016/64 Scope:Global inet6 addr: fe80::a00:27ff:fecd:2016/64 Scope:Link UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1 RX packets:22685771 errors:0 dropped:83424 overruns:0 frame:0 TX packets:13461 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:1604651517 (1.4 GiB) TX bytes:1475694 (1.4 MiB)

Alternatively, use the “ip” command and grep for the promisc flag:

# ip a show eth1 | grep -i promisc 3: eth1: [BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP] mtu 1500 qdisc pfifo_fast state UP qlen 1000

Persistent settings

To set the interface in promiscuous mode persistently; First, edit the ifcfg-ethX file and add “PROMISC=yes” to the end of the options.

# vim /etc/sysconfig/network-scripts/ifcfg-eth1 PROMISC=yes 

Источник
How to check promiscuous mode in linux?
Promiscuous mode enables Sniffers to capture all network traffic. To detect Promiscuous mode in a UNIX type operating system, use the command "ifconfig -a" (without quotes). Search for the PROMISC flag in the output. Other command which can be used to detect is promiscuous mode in UNIX type operating systems "ip link".
How do I know if my NIC supports promiscuous mode?
The only way to experimentally determine whether promiscuous mode is working is to plug your computer into a non-switching hub, plug two other machines into that hub, have the other two machines exchange non-broadcast, non-multicast traffic, and run a capture program such as Wireshark and see whether it captures the .
Which command verifies that the interface is in promiscuous mode?
Use netstat -i to check if interfaces are running in promiscuous mode.
What does promiscuous mode do?
It is a network security, monitoring and administration technique that enables access to entire network data packets by any configured network adapter on a host system. Promiscuous mode is used to monitor(sniff) network traffic.
HakTip - Packet Sniffing 101: Promiscuous Mode

22 related questions found 
Should I use promiscuous mode?
Promiscuous mode must be supported by each network adapter as well as by the input/output driver in the host operating system. Promiscuous mode is often used to monitor network activity. . If it isn't, the data packet is passed onto the next LAN device until the device with the correct network address is reached.
How do I enable promiscuous mode?

Navigate to the environment you want to edit.
Click Settings to open the VM Settings page.
For the network adapter you want to edit, click Edit Network Adapter.
Next to Promiscuous mode, select Enabled. The network adapter is now set for promiscuous mode.

How do I find my ip in Linux?

ifconfig -a.
ip addr (ip a)
hostname -I | awk ''
ip route get 1.2. .
(Fedora) Wifi-Settings→ click the setting icon next to the Wifi name that you are connected to → Ipv4 and Ipv6 both can be seen.
nmcli -p device show.

How do I restart a Linux network?

Use the following command to restart the server networking service. # sudo /etc/init.d/networking restart or # sudo /etc/init.d/networking stop # sudo /etc/init.d/networking start else # sudo systemctl restart networking.
Once this done, use the following command to check the server network status.

What does ifconfig display in Linux?
The “ifconfig” command is used for displaying current network configuration information, setting up an ip address, netmask, or broadcast address to a network interface, creating an alias for the network interface, setting up hardware address, and enable or disable network interfaces.
What is the difference between monitor mode and promiscuous mode?
Unlike promiscuous mode, which is also used for packet sniffing, monitor mode allows packets to be captured without having to associate with an access point or ad hoc network first. . Monitor mode only applies to wireless networks, while promiscuous mode can be used on both wired and wireless networks.
What is tcpdump promiscuous mode?
When tcpdump is run, the interface is put into promiscuous mode, which causes all packets "heard" on that interface to be passed up the network stack for evaluation.
What would you use to sniff traffic on a switch?
What could you use to sniff traffic on a switch? Port mirroring; Port mirroring allows you to capture traffic on a switch port transparently, by sending a copy of traffic on the port to another port of your choosing.
What is the promiscuous mode and give an example?
In promiscuous mode, some software might send responses to frames even though they were addressed to another machine. However, experienced sniffers can prevent this (e.g., using carefully designed firewall settings). An example is sending a ping (ICMP echo request) with the wrong MAC address but the right IP address.
What is promiscuous mode in switch?
Promiscuous mode is a security policy which can be defined at the virtual switch or portgroup level in vSphere ESX/ESXi. A virtual machine, Service Console or VMkernel network interface in a portgroup which allows use of promiscuous mode can see all network traffic traversing the virtual switch.
What happens when a network connection is set to promiscuous mode?
When a network interface is placed into promiscuous mode, all packets are sent to the kernel for processing, including packets not destined for the MAC address of the network interface card.
How do I find the Linux version?

Open the terminal application (bash shell)
For remote server login using the ssh: ssh user@server-name.
Type any one of the following command to find os name and version in Linux: cat /etc/os-release. lsb_release -a. hostnamectl.
Type the following command to find Linux kernel version: uname -r.

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