![]() ![]() Check Device Manager ( devmgmt.msc) to ensure the adapter itself has been uninstalled. If it is present in a more recent installation, it can be removed by running (as Administrator) NPFInstall.exe -ul from the Npcap installation directory (usually C:\\Program Files\\Npcap). This is no longer necessary, and can disrupt network operations in some cases. The data link type for this adapter is DLT_NULL.Įarlier releases of Npcap (before 0.9983) installed a software network adapter called "Npcap Loopback Adapter" for this purpose. ![]() In the list of capture interfaces, select "Adapter for loopback traffic capture" and begin capturing as usual. Npcap adds several new features to those existing in WinPcap, including loopback traffic capture. ![]() Npcap is an update of WinPcap using NDIS 6 Light-Weight Filter (LWF), done by Yang Luo for Nmap project during Google Summer of Code 20. Summary: you can capture on the loopback interface on Linux, on various BSDs including macOS, and on Digital/Tru64 UNIX, and you might be able to do it on Irix and AIX, but you definitely cannot do so on Solaris, HP-UX, or Windows without Npcap. See CaptureSetup/NetworkMedia for Wireshark capturing support on various platforms. You will only see it if you capture on the "loopback interface", if there is such an interface and it is possible to capture on it see the next section for information on the platforms on which you can capture on the "loopback interface". This means that you will not see it if you are trying to capture on, for example, the interface device for the adapter to which the destination address is assigned. If you are trying to capture traffic from a machine to itself, that traffic will not be sent over a real network interface, even if it's being sent to an address on one of the machine's network adapters. ![]() So it's not just about having a loopback interface but strictly about being able to set the desired IP address to it.The following will explain capturing on loopback interfaces a bit. Obviously the 127.0.0.1 IP address cannot be used for any of this, first of all because it's a host local loopback address - the whole 127.0.0.0/8 range is reserved for local loopback - you cannot use it for routing and as traffic source / destinations between hosts. You can do a lot of these things without loopbacks but that requires you to implement kludges and hacks. Router / cluster IDs, iBGP peering backed by an IGP such as OSPF, PIM RPs, MSDP peering, tunnel sources and destinations, NAT sources, VRF targets / identifiers… the uses are a plenty. Most non-trivial routing protocol and NAT setups need loopback addresses for, well, many things, pretty much any network engineer will tell you that. Loopbacks are commonly used as traffic sources and destinations - software can listen on a loopback interface (like it does on 127.0.0.1). From a routing point of view this is important because a route to a loopback IP address will therefore always be active in the routing table. not bound to any NIC) which unless shutdown, are permanently in the "up" state. Some GUI functions don't support loopbacks (say GRE tunnels - you can't specify a loopback-based source of the tunnel), but you're OK using them in bgpd configs, to what loopback interfaces are: they are software-driven interfaces (i.e. Or make it an alias (secondary IP) for lo0. This has been mentioned in this forum before. To the OP: as suggested above, install the shellcmd package (if your platform allows package installation) and add the necessary "ifconfig lo1 create ifconfig lo0 up inet a.b.c.d 255.255.255.255" into early start commands. I think this should be raised as a feature request: allow the creation and control over loopback interfaces. ![]()
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