DHCP - Questions

Hi,

Q: Is it possible to run two DHCP servers on one subnet with each of them
offering a scope that does not overlap?

Q: How do clients actually end up choosing one of them, 1st to respond type
thing?

Q: We notice some of our Vista clients that were static all of sudden now
find a dhcp server automatically and then take a dhcp lease!! Even though we
haven't set it!

You investigate network properies of vista client, and the old static DNS
entries are entered in there !! What is that all about?! {ipv4}

Q: Does anyone know why a dhcp server is able to answer a broadcast DHCP
requests before a router can forward the dhcp relay? Why does the server win
out against a relay agent?

Hello Kyle,

See inline.

Best regards

Meinolf Weber
Disclaimer: This posting is provided "AS IS" with no warranties, and confers
no rights.
** Please do NOT email, only reply to Newsgroups
** HELP us help YOU!!! http://www.blakjak.demon.co.uk/mul_crss.htm

> Hi,
>
> Q: Is it possible to run two DHCP servers on one subnet with each of
> them offering a scope that does not overlap?

Yes, just make sure that the scope does not overlap, so one scope 10.0.0.10
to 10.0.0.125 and a second scope 10.0.0.126 to 10.0.0.250, so you have still
some addresses free.

> Q: How do clients actually end up choosing one of them, 1st to
> respond type thing?

First come, first serve. No way for choosing

> Q: We notice some of our Vista clients that were static all of sudden
> now find a dhcp server automatically and then take a dhcp lease!!
> Even though we haven't set it!

Sorry, if they have only one NIC enabled and you set a fixed ip on it, NOT
possible for my point of view. Please post an unedited ipconfig /all from
one of them.

> You investigate network properies of vista client, and the old static
> DNS entries are entered in there !! What is that all about?! {ipv4}

If you do not uncheck the fixed DNS ip configuration on the NIC they will
stay.

> Q: Does anyone know why a dhcp server is able to answer a broadcast
> DHCP requests before a router can forward the dhcp relay? Why does
> the server win out against a relay agent?

Not clear what you mean, is the DHCP server in the same or another subnet?
You shouldn't use both options in one subnet, either the server or the relay
agent.

Ok thank you for quick reply.

To answer questions

1- Windows Vista reacted this way out of the box.
Not explanation on why, static IP should of stayed, very strange. It's not
GPO either.

2 - To answer your questions regarding unrelated question about relay agent.
This question pertains to our remote offices which have DHCP installed on
branch server. If branch server goes down then the relay agent pics up
request and sends it. It works perfectly -tested! The relay agent goes up
to a branch office which has a standby DEACTIVATED SCOPE availalble at all
times. I was just curious why at the branch the server pics up broadcase
before relay agent routes it.




"Meinolf Weber" wrote:

> Hello Kyle,
>
> See inline.
>
> Best regards
>
> Meinolf Weber
> Disclaimer: This posting is provided "AS IS" with no warranties, and confers
> no rights.
> ** Please do NOT email, only reply to Newsgroups
> ** HELP us help YOU!!! http://www.blakjak.demon.co.uk/mul_crss.htm
>
> > Hi,
> >
> > Q: Is it possible to run two DHCP servers on one subnet with each of
> > them offering a scope that does not overlap?
>
> Yes, just make sure that the scope does not overlap, so one scope 10.0.0.10
> to 10.0.0.125 and a second scope 10.0.0.126 to 10.0.0.250, so you have still
> some addresses free.
>
> > Q: How do clients actually end up choosing one of them, 1st to
> > respond type thing?
>
> First come, first serve. No way for choosing
>
> > Q: We notice some of our Vista clients that were static all of sudden
> > now find a dhcp server automatically and then take a dhcp lease!!
> > Even though we haven't set it!
>
> Sorry, if they have only one NIC enabled and you set a fixed ip on it, NOT
> possible for my point of view. Please post an unedited ipconfig /all from
> one of them.
>
> > You investigate network properies of vista client, and the old static
> > DNS entries are entered in there !! What is that all about?! {ipv4}
>
> If you do not uncheck the fixed DNS ip configuration on the NIC they will
> stay.
>
> > Q: Does anyone know why a dhcp server is able to answer a broadcast
> > DHCP requests before a router can forward the dhcp relay? Why does
> > the server win out against a relay agent?
>
> Not clear what you mean, is the DHCP server in the same or another subnet?
> You shouldn't use both options in one subnet, either the server or the relay
> agent.
>
>
>

Hello Kyle,

Only a thought.

The Relay Agent communicates with a DHCP server and acts as a proxy for DHCP
broadcast messages that must be routed to remote segments. So this will take
more time, then finding the local DHCP server.

Best regards

Meinolf Weber
Disclaimer: This posting is provided "AS IS" with no warranties, and confers
no rights.
** Please do NOT email, only reply to Newsgroups
** HELP us help YOU!!! http://www.blakjak.demon.co.uk/mul_crss.htm

> Ok thank you for quick reply.
>
> To answer questions
>
> 1- Windows Vista reacted this way out of the box. Not explanation on
> why, static IP should of stayed, very strange. It's not GPO either.
>
> 2 - To answer your questions regarding unrelated question about relay
> agent.
> This question pertains to our remote offices which have DHCP
> installed on
> branch server. If branch server goes down then the relay agent pics
> up
> request and sends it. It works perfectly -tested! The relay agent
> goes up to a branch office which has a standby DEACTIVATED SCOPE
> availalble at all times. I was just curious why at the branch the
> server pics up broadcase before relay agent routes it.
>
> "Meinolf Weber" wrote:
>
>> Hello Kyle,
>>
>> See inline.
>>
>> Best regards
>>
>> Meinolf Weber
>> Disclaimer: This posting is provided "AS IS" with no warranties, and
>> confers
>> no rights.
>> ** Please do NOT email, only reply to Newsgroups
>> ** HELP us help YOU!!! http://www.blakjak.demon.co.uk/mul_crss.htm
>>> Hi,
>>>
>>> Q: Is it possible to run two DHCP servers on one subnet with each
>>> of them offering a scope that does not overlap?
>>>
>> Yes, just make sure that the scope does not overlap, so one scope
>> 10.0.0.10 to 10.0.0.125 and a second scope 10.0.0.126 to 10.0.0.250,
>> so you have still some addresses free.
>>
>>> Q: How do clients actually end up choosing one of them, 1st to
>>> respond type thing?
>>>
>> First come, first serve. No way for choosing
>>
>>> Q: We notice some of our Vista clients that were static all of
>>> sudden
>>> now find a dhcp server automatically and then take a dhcp lease!!
>>> Even though we haven't set it!
>> Sorry, if they have only one NIC enabled and you set a fixed ip on
>> it, NOT possible for my point of view. Please post an unedited
>> ipconfig /all from one of them.
>>
>>> You investigate network properies of vista client, and the old
>>> static DNS entries are entered in there !! What is that all about?!
>>> {ipv4}
>>>
>> If you do not uncheck the fixed DNS ip configuration on the NIC they
>> will stay.
>>
>>> Q: Does anyone know why a dhcp server is able to answer a broadcast
>>> DHCP requests before a router can forward the dhcp relay? Why does
>>> the server win out against a relay agent?
>>>
>> Not clear what you mean, is the DHCP server in the same or another
>> subnet? You shouldn't use both options in one subnet, either the
>> server or the relay agent.
>>