Releasing all addresses to change subnet mask

[Maritime]

Hi
I'm currently using DHCP and my leases were set to unlimited (Not to expire). I now want to change my subnet mask to increase the number of addresses available on the network. The question is how can I flush all the existing leases and have each user obtain new ones one the subnet is changed? Will just changing the option from unlimited to limited in DHCP manager cause the leases to expire? Thanks in advance.

 

[rwullems]

Normally changing the lease time will not help you in this situation. A client will check the DHCP server at 50%, 87,5% and finally at 100% of it lease time to see if he may renew the lease. In your case, the lease never expires. I have never tried it myself, but i can imagene that in that case the client, ones obtained an ip address doesn't need to contact the DHCP server anymore.

If you have somekind of sniffing tool, try capturing the traffic between a client that is booting up and the DHCP server, if there is any, it will probably be an DHCP inform message comming from the client and a ACK comming from the server.

If this is the case, your option will be changing the scoop, reboot al your clients, the server will then send a NACK to the client as an answer to the inform message, forcing the client to renew it's lease, obtaining address from your new scoop.
regards,
Robert


Robert Wullems
Technical Instructor
SCM/CNX/MCSA/Network+
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If you can Sniff it, you can solve it!
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[Maritime]

I was actually thinking the same thing as you expressed, I will check my logs to check on the NACK. Thanks for the feedback.

 

[peterve]

I don't know how many machines you are talking about, and if they are in your building..; but a simple ipconfig /release and ipconfig /renew might come handy as well

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