clarification on dhcp

hai

Can anyone tell me that if i am having two dhcp servers running on
same network
on two different machines. If i run a client in the same network. Then
to which server the client will respond to.And how this case is delt
in dhcp.

* and also send me the various test cases that can be applied to test
the dhcp client.

Thanking you,
K.RajaSekhar

On 2005-04-03, RajaSekhar.Kavuri <(E-Mail Removed)> wrote:
> Can anyone tell me that if i am having two dhcp servers running on
> same network

If you have two dhcp server you have a problem. Both will try to
respond to requests and all the clients will become very confused
machines.
Davide

--
Why use Windows, since there is a door?

Davide Bianchi wrote:

> On 2005-04-03, RajaSekhar.Kavuri <(E-Mail Removed)> wrote:
>> Can anyone tell me that if i am having two dhcp servers running on
>> same network
>
> If you have two dhcp server you have a problem. Both will try to
> respond to requests and all the clients will become very confused
> machines.

That is incorrect. Many business lans have multiple dhcp servers. When a
computer requests a lease, any dhcp server can respond. The computer then
accepts the first lease it's offered and ignores the rest. The only
concern is that the dhcp servers don't try to offer addresses already in
use. This can be avoided, by assigning each dhcp server, it's own pool of
addresses, out of the total available. Incidentally, multiple dhcp servers
can also provide a crude form of load balancing, where each server will
specify a different dns server or default gateway, when multiple choices
are available.

Davide Bianchi <(E-Mail Removed)> wrote:

> On 2005-04-03, RajaSekhar.Kavuri <(E-Mail Removed)> wrote:
>> Can anyone tell me that if i am having two dhcp servers running on
>> same network
>
> If you have two dhcp server you have a problem. Both will try to
> respond to requests and all the clients will become very confused
> machines.

DHCP allows for more than one server on the same LAN. The
client selects just one. See RFC2131 chapter 3.1.

However how it is secured that no IP is duplicatly leased is
another problem(1). Thus, if possible I would avoid such a
scenario.


Ciao, Horst

(1) I don't remember whether this problem is explicitely
addressed in the RFC and I'm too lazy to read it again
at the moment. ;-)
--
»When pings go wrong (It hurts me too)« E.Clapton/E.James/P.Tscharn

(E-Mail Removed) (RajaSekhar.Kavuri) wrote in
news:(E-Mail Removed) om:

> on two different machines. If i run a client in the same network. Then
> to which server the client will respond to.And how this case is delt
> in dhcp.
>

When your client wants an IP address, it sends out a DHCPREQUEST packet
with a destination address of 255.255.255.255 (aka, a broadcast). Any DHCP
server that receives that request can reply to it with an offer. Of all
the offers that come in, the client chooses one and sends the server that
offer came from an acknowledgement that it will take it.

As others have said, the problem can come about if two servers are both
offering the same addresses. If neither are aware of the other, they could
both hand out, for example, 192.168.0.100, causing an IP conflict.
Provided both servers are not giving out the same IPs, you can run both at
once.

Horst Knobloch wrote:

> However how it is secured that no IP is duplicatly leased is
> another problem(1). Thus, if possible I would avoid such a
> scenario.

The easiest way, would be to give each dhcp server it's own address pool.
For example, if your dhcp range is x.x.x.1 to x.x.x.254, you could give one
dhcp server the addresses from x.x.x.1 to x.x.x.127 and the 2nd dhcp server
the range from x.x.x.128 to x.x.x.254.