2 DHCP Servers leasing same address ranges

Hi,

If I have 2 DHCP servers with scopes leasing same address range, it is
possible that other DHCP server leases address that other server has allready
leased to some computer or are dhcp servers aware of each other so that other
server knows that some address is already leased by another dhcp-server.
--
Petri S

"Petri S" <(E-Mail Removed)> ha scritto nel messaggio
news:5DFB1399-6582-4A07-AC44-(E-Mail Removed)...
> Hi,
>
> If I have 2 DHCP servers with scopes leasing same address range, it is
> possible that other DHCP server leases address that other server has
> allready
> leased to some computer or are dhcp servers aware of each other so that
> other
> server knows that some address is already leased by another dhcp-server.
> --
> Petri S

Since the DHCP initialization and renewal processes are made broadcasting
the nwtwork to search for any DHCP Server available, I thnk that any
authorized DHCP can reply trying to assingn/renew an IP address.

If you are you in A.D. domain, all DHCP servers must be authorized and have
their scopes activated to be enabled to service the network

Even though this doesn't mean they are aware of each other.

A best practice of DHCP is the "80/20 rule": you plan to use 2 servers just
in case 1 goes down and assign 80% of address range to the first DHCP and
the remaining 20% to the other. Don't forget to apply exclusions to each
other scopes! Otherwise you risk to mess up the network.

I hope this helps you.

Bye
MD

"Petri S" <(E-Mail Removed)> ha scritto nel messaggio
news:5DFB1399-6582-4A07-AC44-(E-Mail Removed)...
> Hi,
>
> If I have 2 DHCP servers with scopes leasing same address range, it is
> possible that other DHCP server leases address that other server has
> allready
> leased to some computer or are dhcp servers aware of each other so that
> other
> server knows that some address is already leased by another dhcp-server.
> --
> Petri S

This is technically possible if the client releases the IP address (through
a proprer shutdown or ipconfig /release) and then asks for a new IP address.
In the DHCP renewal process instead, the DHCP Client contacts directly the
same DHCP server that assigned its IP to get the lease renewal.

Since the DHCP initialization process is made broadcasting
the network to search for any DHCP Server available, any
authorized DHCP can reply trying to assingn/renew an IP address.
The first server that ends successfuly the DHCP discover, offer, Request and
acknowledgement, assigns the dhcp clien a new IP address.

This means that any DHCP server is challenged to end that process first.

A best practice of DHCP is the "80/20 rule": you plan to use 2 servers just
in case 1 goes down and assign 80% of address range to the first DHCP and
the remaining 20% to the other. Don't forget to apply exclusions to each
other scopes! Otherwise you could mess up the network.

I hope this helps you.

Bye
MD

I think also that you could increase the "conflict detection" value to avoid
a different DHCP to assign an already booked IP address. This however
increases the network traffic and should not be taken into account as a best
practice, I think.

Bye

MD