DHCP query

Simon Hobson dhcp1 at thehobsons.co.uk
Wed Apr 18 08:59:38 UTC 2012

ameen.shajahan at wipro.com wrote:

>Started the DHCP server in server side.
>Gave ipconfig /renew in client(PC) , IP address assigned to client PC .
>Then I stopped the DHCP server(dhcpd) in server side and gave 
>ipconfig in client side to check whether it has the assigned 
>IPaddress by the dhcp server. Yes client has IP address still.

That is correct.
When the server issues a lease, it basically tells the client "you 
can use this address (and other settings), and you can have it until 
<some time>". Until that time arrives, the client is free to use that 
lease without further reference to the server. If the client has 
persistent storage and real time clock, it can even keep that address 
across restarts.

After a period, typically about half the lease time) the client will 
attempt to renew the lease. Even when it gets no reply, it can still 
continue using the address. It only has to stop when the lease 
expires - at which point the client will remove the address and stop 
using it, and if it's failed to get another address then it will lose 

I strongly suggest you track down the book "The DHCP Handbook" by 
Ralph Droms and Ted Lemon. ISBN 9781578701377 for the first edition, 
though there is a second edition out.
This explains everything you've asked and a lot more besides 
(including the historical context of why some things are done as they 
are) - and it's very readable too.

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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