Mac OS X ipconfig

If you momentarily forget where you are at a Mac OS X terminal session, you might type "ipconfig /all" or something equally Windowish. You will get a response:

usage: ipconfig <command> <args>>
where <command> is one of waitall, getifaddr, ifcount, getoption, getpacket, set, setverbose

What's this? You already know you mistyped: on Mac OS X you probably meant to run "ifconfig -a" just as you would on Linux. But "ipconfig" is different, and is actually something good to have in your bag of tricks.

The first thing ipconfig can do for you is quickly give you all your dhcp info:

$ ipconfig getpacket en0
op = BOOTREPLY
htype = 1
flags = 0
hlen = 6
hops = 0
xid = 1045997387
secs = 0
ciaddr = 0.0.0.0
yiaddr = 192.168.9.30
siaddr = 0.0.0.0
giaddr = 0.0.0.0
chaddr = 0:16:cb:8d:38:f7
sname =
file =
options:
Options count is 7
dhcp_message_type (uint8): ACK 0x5
subnet_mask (ip): 255.255.255.0
lease_time (uint32): 0x93a80
router (ip_mult): {192.168.9.254}
domain_name_server (ip_mult): {192.168.9.254}
server_identifier (ip): 192.168.9.254
end (none):

There are shortcuts to the items listed under "options":

$ ipconfig getoption en0 router
192.168.9.254
$ ipconfig getoption en0 domain_name_server
192.168.9.254

"ipconfig getifaddr en0" is a quick way to just get the ip address. You can also use ipconfig with its "set" options to change an interface from DHCP to manual or vice-versa. That's temporary; it doesn't write any start up files.

If you are having difficulty with DHCP, ipconfig has one more use: you can (as root) set verbose logging with "ipconfig setverbose 1". With that set, you get minor debugging info written to syslog (/var/log/system.log on my system) , but you also get a separate BOOTP/DHCP log in /var/log/com.apple.IPConfiguration.bootp that shows the full BOOTREQUEST/BOOTREPLY packet negotiation.

Think of ipconfig the next time you are looking for DHCP info on a Mac.

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