macOS SierraにHomebrewでipコマンドをインストールする ref: http://qiita.com/ponsuke0531/items/bb10e2a8614501f51723

file0.txt

$ brew upgrade
Updating Homebrew...
==> Auto-updated Homebrew!
<省略>

$ brew doctor
Your system is ready to brew.

file1.txt

$ brew search iproute2mac
iproute2mac

file2.txt

$ brew install iproute2mac
==> Using the sandbox
==> Downloading https://github.com/brona/iproute2mac/releases/download/v1.2.1/iproute2mac-1.2.1.tar.gz
==> Downloading from https://github-production-release-asset-2e65be.s3.amazonaws.com/24814763/10faf55c-
######################################################################## 100.0%
🍺  /usr/local/Cellar/iproute2mac/1.2.1: 6 files, 21KB, built in 4 seconds

file3.txt

$ ip
Usage: ip [ OPTIONS ] OBJECT { COMMAND | help }
       ip -V
where  OBJECT := { link | addr | route | neigh }
       OPTIONS := { -4 | -6 }

iproute2mac
Homepage: https://github.com/brona/iproute2mac
This is CLI wrapper for basic network utilities on Mac OS X inspired with iproute2 on Linux systems.
Provided functionality is limited and command output is not fully compatible with iproute2.
For advanced usage use netstat, ifconfig, ndp, arp, route and networksetup directly.

$ ip -V
iproute2mac, v1.2.1