Self-Study Deep Dive: ifconfig

#networking #ifconfig #ip #loopback #nic

Relevant terms

NIC: Network Interface Cards:

LAN vs WAN vs The Internet

LAN: Local Area Network – communications between consecutive devices such as in schools, hospitals, institutions

WAN: Wide Area Network – interconnects multiple LAN to allow shared access to apps, services, other centrally located resources, i.e. connecting between enterprise headquarters, branch offices, facilities, cloud, etc. Eliminates need to install the same application server, firewall, or etc. resource in multiple locations.

The Internet: global communication system, including hardware and infrastructure, using TCP/IP to transmit data via various media types between networks. Connected by guided, wireless, fire-optic tech.

World Wide Web is one of the services communicated over the internet.

Internet Services: include communication services (mail, mailing list, telnet, IM), information retrieval services (FTP, Gopher, Archie, VERONICA), Web services (app interaction), Video Conferencing.

lo0 = loopback interface: allows server/client processes on a single system to communicate with each other w/o interference of NIC. Also known as 127.0.0.1 or localhost.

Using ifconfig lo0 to examine this gives me:

lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384 options=1203<RXCSUM,TXCSUM,TXSTATUS,SW_TIMESTAMP> inet 127.0.0.1 netmask 0xff000000 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 nd6 options=201<PERFORMNUD,DAD>

So I tried to ping 127.00.01 and it was successful, implying that the TCP/IP software stack on my machine is successfully loaded and working.

The loopback is used for troubleshooting or when “a server offering a resource you need is running on your own machine”, i.e. running a webserver.

gif0

is a “generic tunnelling device for IPv4 and IPv6”. Virtual.

stf0

interface supporting 6to4, an internet transition mechanism for migrating from IPv4 to IPv6 via encapsulation (can tunnel IPv6 traffic over IPv4).

enX where X is a num

refers to physical network interfaces. en0 is the first device to start — your wifi. The rest are (likely) Thunderbolt interfaces on a MacOS.

ap1

???

awdl0

is the Apple Wireless Direct Link, typically used for Hotspot functionality

llw0

brdige0

Thunderbolt bridge for transferring files over cable between two Macs.

utunX where X is a num

are related to sharing info between devices on the same iCloud account, also created by any VPN interfaces.

Follow-Up Questions