How Do You Release A DHCP Address on the Outside?

Answered Question
Apr 29th, 2008
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How do you release the address on an ASA-5505 configured to grab an address from the ISP's DHCP server? I can't find a command anywhere, or anything in ASDM.

Correct Answer by srue about 9 years 1 month ago

under the outside vlan interface of the asa5505, you can assign a non-bia mac-address. assign it the same mac as your other router - if you know what that is. that way your ISP won't even realize you've been swapping gear on the line.

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jsoudah Tue, 04/29/2008 - 14:35
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No I didn't try that, but why would either one of those release an IP address? I'd be happy if it works though.

sundar.palaniappan Tue, 04/29/2008 - 15:29
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I don't know of a clear command to force the interface to release the DHCP learned address. Can you try the interface command 'no ip address dhcp' and to reenable dhcp 'ip address dhcp'.


HTH


Sundar

cisco24x7 Tue, 04/29/2008 - 18:12
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Very simple solution. I've tried with my Comcast cable modem provider and it works.


config t

interface e0

no ip address dhcp

shutdown

ip address 1.1.1.1 255.255.255.0

no shut

(wait for about 30 seconds)

no ip address

shut

(wait for 30 seconds)

no shut

ip address dhcp setroute


Now you will have a different IP address

jsoudah Wed, 04/30/2008 - 09:15
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Thanks for the replies. I ended up trying something similar but it didn't break the lease on the ISP's DHCP server.


The reason I wanted to release it was because I was swapping devices back and forth for testing reasons, and if the address isn't released the other device won't get one. The other Verizon/Actiontec router has an address release option, so I just used that every time I wanted to break the lease and switch to the ASA. With the ASA it seems like you either have to ask the ISP to do it or just wait for the lease to expire.

Correct Answer
srue Wed, 04/30/2008 - 18:44
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under the outside vlan interface of the asa5505, you can assign a non-bia mac-address. assign it the same mac as your other router - if you know what that is. that way your ISP won't even realize you've been swapping gear on the line.

rextillojr Wed, 04/30/2008 - 21:35
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Hi,


Reenter this command to reset the DHCP lease and request a new lease:


ip address dhcp [setroute]


Note:

Make sure first that interface is enabled with the "no shutdown" command.


Regards,

Rex Tillo

jsoudah Thu, 05/01/2008 - 10:00
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Srue, good thinking don't know why I didn't think of that before.


rextillojr, I didn't want to renew the lease, just release it.


Thanks to eveyone for their help.

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