DHCP Lease Renew ONLY Via Terminal

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Level 1

5 points

DHCP Lease Renew ONLY Via Terminal

We are replacing our DHCP server with a new applicance. I would like to create a script that would do the exact same thing as the "Renew DHCP Lease" button does in network preferences. I have used Instraments, top, etc to try to isolate the command but have not had any success. My biggest concern is to not interupt the network connection when renewing the DHCP lease. When the "Renew DHCP Lease" button is clicked, my network connection is not dropped.

The only solution I have found for this is to run "ipconfig set enx BOOTP ; ipconfig set enx DHCP" which drops the network.

Does anyone know what command the "Renew DHCP Lease" button preforms or a good way to renew a DHCP lease without dropping the connection.

Posted on Nov 7, 2012 2:30 PM

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Answer 1

g_wolfman

Level 4

3,502 points

Nov 7, 2012 4:31 PM in response to jbNco

networksetup -setdhcp <networkservice> [clientid]

<networkservice> is the name of your interface, usually something like "Wi-Fi", "Ethernet", "Built-in Ethernet" or so on.

[clientid]

is usually optional, unless your ISP or IT section actually requires them (in which case you can always just get it from the Pane in the first place). You can find the proper names for the interfaces using

networksetup -listallnetworkservices

And find all the info about a given network service using

networksetup -getinfo <networkservice>

networksetup is the command line tool for which the Network Preference Pane is the front-end. If scripting, you need to be aware that networksetup will need administrator privileges to renew the DHCP lease (in the Preference Pane, you need to unlock the Pane before you can use the advanced preferences, so it isn't necessarily obvious).

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Answer 2

jbNco Author

Level 1

5 points

Nov 8, 2012 7:24 AM in response to g_wolfman

Thanks Wolfman for responding.

I have tried the command networksetup -setdchp <networkservice> and it has not been updating my lease. The files located at /var/db/dhcpclient/leases do not update for the interface I specify.

Our admin of the current system just updated our lease time to 7200 seconds down from 604800 seconds and this is not updating as well.

Is anyone aware of where I can find a dhclient for Mac OS X?

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Answer 3

chymb

Level 1

0 points

Jan 2, 2013 5:20 PM in response to jbNco

It looks like the button creates a key in System Configuration which causes the configd to renew the lease without dropping the connection. One can create that key via:

echo "add State:/Network/Interface/en0/RefreshConfiguration temporary" | sudo scutil

Cheers,

Chris

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