![]() However, some network interfaces don't support promiscuous mode, and some OSes might not allow interfaces to be put into promiscuous mode. Wireshark will try to put the interface on which it's capturing into promiscuous mode unless the "Capture packets in promiscuous mode" option is turned off in the "Capture Options" dialog box, and TShark will try to put the interface on which it's capturing into promiscuous mode unless the -p option was specified. Most network interfaces can also be put in "promiscuous" mode, in which they supply to the host all network packets they see. multicast packets sent to a multicast address that the host has configured the interface to accept.packets sent to one of that host's link-layer addresses. ![]() Normally, network interfaces supply to the host only: If your machine is not plugged into a switched network or a dual-speed hub, or it is plugged into a switched network but the port is set up to have all traffic replicated to it, the problem might be that the network interface on which you're capturing doesn't support "promiscuous" mode, or because your OS can't put the interface into promiscuous mode. If you have a box of that sort, that has a switch with some number of Ethernet ports into which you plug machines on your network, and another Ethernet port used to connect to a cable or DSL modem, you can, at least, sniff traffic between the machines on your network and the Internet by plugging the Ethernet port on the router going to the modem, the Ethernet port on the modem, and the machine on which you're running Wireshark into a hub (make sure it's not a switching hub, and that, if it's a dual-speed hub, all three of those ports are running at the same speed. Note also that many firewall/NAT boxes have a switch built into them this includes many of the "cable/DSL router" boxes. (Note that it's a Wiki, so you can update or fix that information, or add additional information on those switches or information on new switches, yourself.) See the switch reference page on the Wireshark Wiki for information on some switches. ![]() You would have to check the documentation for the switch to see if this is possible and, if so, to see how to do this. ![]() Some switches have the ability to replicate all traffic on all ports to a single port so that you can plug your analyzer into that single port to sniff all traffic. This problem has also been reported for Netgear dual-speed hubs, and may exist for other "auto-sensing" or "dual-speed" hubs. Note also that on the Linksys Web site, they say that their auto-sensing hubs "broadcast the 10Mb packets to the port that operate at 10Mb only and broadcast the 100Mb packets to the ports that operate at 100Mb only", which would indicate that if you sniff on a 10Mb port, you will not see traffic coming sent to a 100Mb port, and vice versa. Note that even if your machine is plugged into a hub, the "hub" may be a switched hub, in which case you're still on a switched network. Q 7.1: When I use Wireshark to capture packets, why do I see only packets to and from my machine, or not see all the traffic I'm expecting to see from or to the machine I'm trying to monitor?Ī: This might be because the interface on which you're capturing is plugged into an Ethernet or Token Ring switch on a switched network, unicast traffic between two ports will not necessarily appear on other ports - only broadcast and multicast traffic will be sent to all ports. Here is a detailed answer about what traffic you may see that I found on this site 7.
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