newbies questions

Simon Hobson simon at
Mon Oct 21 13:42:32 UTC 2013

"Pol Hallen" wrote:
>I done this question because a client on my lan has many problems: dhcp
>server has this client with fixed ip but I don't know why, client take old
>IP address (IP in the file /var/lib/dhcp/dhcpd.leases)

That can be a problem - is it Windows by any chance ?

If the client asks for a specific address, and its still available for it to use, then the server will still hand it out even if there is a fixed address declaration for it. If the client just does a DHCP-Discover then it'll be offered the fixed address.
Windows clients are particularly bad and try quite hard to get the last address they had. Basically it look slike Microsoft decided to "do their own thing" - the server doesn't follow the RFC in terms of cleint-address match retension, but they made the client do that part instead.

Telling the client to release it's lease and then ask for a new one may work. Even removing the lease from the leases file (or removing the leases file) won't neccessarily fix it. One thing that *will* fix it is to remove the problem address from the pool (so it's no longer available for lease renewals) and wait until the lease expires. For a faster fix, put the address in a pool of it's own and add "deny booting" to the pool - on the next lease renewal, the client request will be denied and it'll have to ask for a new address.

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