General technical discussions.
New Member
Sun Aug 22, 2010 1:53 am

what is promiscuous mode and why its useful in switched LAN?

Mon Jan 29, 2018 11:53 am

i have read about promiscuous mode, it states in most places that it lets a NIC process frames that have a different MAC dest address than the one the NIC is having, having said that, how is it useful in a switched LAN where each host sits in his own collision domain?

if i activate promiscuous mode in a host that is connected to the switch im not supposed to get frames that isnt carrying my dest mac anyway, so is it only useful for networks with hosts that share the same collision domain, like WLAN?
can anyone clarify?

New Member
Sun Mar 13, 2016 2:12 pm

Re: what is promiscuous mode and why its useful in switched

Wed Jun 26, 2019 1:02 pm

In a network, promiscuous mode allows a network device to intercept and read each network packet that arrives in its entirety. This mode of operation is sometimes given to a network snoop server that captures and saves all packets for analysis (for example, for monitoring network usage).

In an Ethernet local area network (LAN), promiscuous mode is a mode of operation in which every data packet transmitted can be received and read by a network adapter. 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.Promiscuous mode is the opposite of non-promiscuous mode. When a data packet is transmitted in non-promiscuous mode, all the LAN devices "listen to" the data to determine if the network address included in the data packet is theirs. If it isn't, the data packet is passed onto the next LAN device until the device with the correct network address is reached. That device then receives and reads the data.
Edwin S |Tech Support Team


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