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Typing ifconfig on the command line gives me listings for several devices. I've seen at least the following ones:

  • lo0
  • gif0
  • stf0
  • en0
  • en1
  • en2
  • en3
  • p2p0
  • awdl0
  • bridge0

What specifically do each of them refer to? I know en0 is a wireless connection, en3 is a connection using a Thunderbolt-to-ethernet adapter, and en1 is an ordinary ethernet connection. What about the rest?

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  • If your first discovered network interface is WiFi, en0 would be wireless, but Macs with physical wired Ethernet have en0 as wired in most cases.
    – bmike ♦
    Commented Oct 22, 2015 at 16:12

2 Answers 2

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7

These are properly known as BSD names, so you can look at the BSD / Darwin source code to see what these mean.

  • en is Ethernet
  • lo is loop back or local host
  • awdl is air drop peer to peer (a type of mesh network)
  • bridge is a connection between networks
  • p2p is sometimes a virtualization link and also some people have reported it being used with AirDrop before that changed to be awdl0

The numbers added to the end just increment as you add a second interface of the same type. The rest are tunneling interfaces for VPN and bridging between IPv4 and IPv6:

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  • Not all en refer to a wired ethernet connection. Are wireless connections considered a form of ethernet? (If so, how?)
    – jvriesem
    Commented Oct 22, 2015 at 16:24
  • 1
    @jvriesem The media section will let you know if an Ethernet connection uses wired connections in most cases (and which flavor) - the en tag commingles both wired and wireless hardware.
    – bmike ♦
    Commented Oct 22, 2015 at 16:31
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The -v flag provides a type info on some interfaces, for example IP over Thunderbolt for en2:

ifconfig -v en2                              
en2: flags=8963<UP,BROADCAST,SMART,RUNNING,PROMISC,SIMPLEX,MULTICAST> mtu 1500 index 6
    eflags=41000080<TXSTART,ECN_ENABLE,FASTLN_ON>
    options=460<TSO4,TSO6,CHANNEL_IO>
    ether 82:02:9f:a3:0c:00 
    netif: EF77BC13-3B69-466C-8BA2-591CCA2D6C44
    flowswitch: C155EE61-3E2C-465E-9AFB-17C36ECD8F8C
    media: autoselect <full-duplex>
    status: inactive
    type: IP over Thunderbolt
    agent domain:Skywalk type:NetIf flags:0xa443 desc:"Userspace Networking"
    agent domain:Skywalk type:FlowSwitch flags:0x4403 desc:"Userspace Networking"
    state availability: 0 (true)
    scheduler: FQ_CODEL 
    qosmarking enabled: yes mode: none
    low power mode: disabled
    multi layer packet logging (mpklog): disabled
    routermode4: disabled
    routermode6: disabled
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