where to get the lease file

[liu.renfeng]

Thanks for all the Wonderful discuss. So what I need to do is touching a lease file?




Best Regards,
Robin 
 
Tel: +86-27-8761-7326 Ext: 309
2006-11-23



发件人： Luciano Miguel Ferreira Rocha
发送时间： 2006-11-23 06:36:02
收件人： busybox at busybox.net
抄送： 
主题： Re: where to get the lease file

On Wed, Nov 22, 2006 at 10:04:40PM +0100, Denis Vlasenko wrote:
> On Wednesday 22 November 2006 19:11, Luciano Miguel Ferreira Rocha wrote:
>  >  > It isn't very informative, and usually I've found that a lot of INIT scripts
>  >  > will remove the existing file and "touch" a new file in it's place as part
>  >  > of the system startup..
>  > 
>  > If you're talking about clients, then I see no problem with that. But
>  > with servers, that's wrong (unless in an embedded system without
>  > permanent storage).
>  > 
>  > That file is only available source of current leases. So, in
>  > order to prevent assignment to clients of IP addresses already in use,
> 
> Why do you want to preserve that? The whole point of DHCP is that addresses
> are dynamic. They can change. Anyone sitting on DHCP ought to be ready
> for the fact that on each reboot (of DHCP client) [s]he can get
> different IP.

Yes, but it isn't nice on the network to have clients change their IP
addresses willy-nilly. There's things like smb announcements, mDNS,
dynamic DNS and existing TCP sessions that will have to be broken.

> DHCP server should try hard to not assign IP address which is already taken.
> It can be done by sending ARP probes before you hand out new IP
> to new client. Lease file is not needed for that.

That just doesn't work on a large network. Note that I don't know which
server was being used on that instance, but it was based on probes for
taken addresses.

And also for those cenarios like two clients asking for the same IP to a
just started server (it's conceivable, but extremely unlikely).

It's just good practice. But also unavailable on some embedded systems.
I was just trying to explain the practice, not mandating it.

-- 
lfr
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