Query on DHCPINFORM message

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Query on DHCPINFORM message

muneer-2
Hi,

   I need a clarification on DHCP inform message. Is it applicable
only to manually configured hosts? Can I use it in the following
scenario?

I have a host which got IP address through DHCP. Its renewal is after
10 days. On the first day I added some more options in the server. Can
I send an Inform message from the client to get these updated options?
Is it a violation to the standards?

--
Imagination is more important than knowledge...

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Re: Query on DHCPINFORM message

Andre Kostur-2
Muneer wrote:
>    I need a clarification on DHCP inform message. Is it applicable
> only to manually configured hosts? Can I use it in the following
>  

No, I've seen it used on dynamic hosts.

> scenario?
>
> I have a host which got IP address through DHCP. Its renewal is after
> 10 days. On the first day I added some more options in the server. Can
> I send an Inform message from the client to get these updated options?
>  

No.  DHCPINFORM is a client->server message.  You want DHCPFORCERENEW
(althought I don't know anybody who implements it yet).

> Is it a violation to the standard?

Yes.  You want the message to go the wrong way.

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Re: Query on DHCPINFORM message

muneer-2
On 12/5/05, Andre Kostur <[hidden email]> wrote:
> Muneer wrote:
> >    I need a clarification on DHCP inform message. Is it applicable
> > only to manually configured hosts? Can I use it in the following
> >
>
> No, I've seen it used on dynamic hosts.

Can you give an example situation where client needs to send inform
message? Dynamic host will aquire IP through dhcp. This mesage
sequence itself is used to get the remaining parameters also. So where
does it need to send the INFORM message separately?

>
> > scenario?
> >
> > I have a host which got IP address through DHCP. Its renewal is after
> > 10 days. On the first day I added some more options in the server. Can
> > I send an Inform message from the client to get these updated options?
> >
>
> No.  DHCPINFORM is a client->server message.  You want DHCPFORCERENEW
> (althought I don't know anybody who implements it yet).
>
> > Is it a violation to the standard?
>
> Yes.  You want the message to go the wrong way.
>

I think you have mistaken my question. Administrator configures the
new parameter in the server. He wants the client to be updated. So he
goes to the client and forces the client to send an INFORM message to
the server. Is this legal? Or is he suppose to send a renew message
(like force renew)?


--
Imagination is more important than knowledge...

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Re: Query on DHCPINFORM message

Andre Kostur-2
Muneer wrote:

> On 12/5/05, Andre Kostur <[hidden email]> wrote:
>  
>> Muneer wrote:
>>    
>>>    I need a clarification on DHCP inform message. Is it applicable
>>> only to manually configured hosts? Can I use it in the following
>>>
>>>      
>> No, I've seen it used on dynamic hosts.
>>    
>
> Can you give an example situation where client needs to send inform
> message? Dynamic host will aquire IP through dhcp. This mesage
> sequence itself is used to get the remaining parameters also. So where
> does it need to send the INFORM message separately?
>  

As I recall, some version of the Novell Netware client on Windows needed
some of the options that were being returned by the DHCP sever, but the
Netware client couldn't (or wouldn't) access the original response.  So
after the device obtained an address, the Netware client would emit the
DHCPINFORM to solicit a response to itself so it could read the
appropriate options.

>>> scenario?
>>>
>>> I have a host which got IP address through DHCP. Its renewal is after
>>> 10 days. On the first day I added some more options in the server. Can
>>> I send an Inform message from the client to get these updated options?
>>>
>>>      
>> No.  DHCPINFORM is a client->server message.  You want DHCPFORCERENEW
>> (althought I don't know anybody who implements it yet).
>>
>>    
>>> Is it a violation to the standard?
>>>      
>> Yes.  You want the message to go the wrong way.
>>
>>    
>
> I think you have mistaken my question. Administrator configures the
> new parameter in the server. He wants the client to be updated. So he
> goes to the client and forces the client to send an INFORM message to
> the server. Is this legal? Or is he suppose to send a renew message
> (like force renew)?
>  
Whups... I did misread.  Somehow I read that you wanted to send the
Inform _to_ the client.  My mistake.

Yes, you could send an inform from the client to the server to get the
new options.  A renew would probably accomplish the same thing (and is
guaranteed to already be implemented on the client...).  I think most
people would just have the client renew.

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Re: Query on DHCPINFORM message

David W. Hankins
In reply to this post by muneer-2
On Mon, Dec 05, 2005 at 05:13:10PM +0530, Muneer wrote:
> Can you give an example situation where client needs to send inform
> message? Dynamic host will aquire IP through dhcp. This mesage
> sequence itself is used to get the remaining parameters also. So where
> does it need to send the INFORM message separately?

It may not in fact be the operating system at all.

Some http clients look for DHCP options the host operating system doesn't
know to put in its requested options list.

So, these user-space applications send their own INFORM once they've
been loaded by the user.

The advantage being that they can do so to acheive DHCP configuration
options without interfering with the lease expiration time.


Of course it would be nice if the host operating system learned to ask,
since there is no timer for refreshing information discovered via INFORM.

--
David W. Hankins "If you don't do it right the first time,
Software Engineer you'll just have to do it again."
Internet Systems Consortium, Inc. -- Jack T. Hankins

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