DHCP failover:is cluster a good option ?

[Marlon Brown]

I want to provide failover to DHCP servers.
Is the cluster alternative on Win2003 Ent Server a good way to go ? I have
been reading documentation and I see that MS DHCP is cluster aware, I just
want to know if the cluster solution is practical and works without many
problems.

 

[Steven L Umbach]

Hi Marlon.

I am no means a clustering expert, and have not actually implemented what
you propose, but I am sure that would work if you can afford the expense
building the cluster and having one server standing by and having shared
storage between the two servers. However also take a look at the link below
with using two dhcp servers with the 80/20 rule of allocating IP addresses
between scopes keeping in mind that while that may not be able to service
your whole network on a long term basis with the default lease time of eight
days if would probably give you a couple days to get the main dhcp server
back online. --- Steve

http://www.microsoft.com/resources/.../proddocs/en-us/sag_dhcp_imp_ConfigScopes.asp
http://tinyurl.com/6zdmr -- same link, shorter.

 

[Phillip Windell]

You don't need any clusters.

Just configure two DHCP Servers. Configure the DHCP service with exaclty
identical Scopes. The only thing different is that you create and arrange
the Exclusions so that each server gives out one-half of the available
addresses.

If one DHCP dies, you simply remove the extra Exclusion from the remaining
Server so that it can now give out all the available address and it will
keep things going while the other is repaired. When the dead DHCP is
repaired, you just put the Exclusions back the way they were.

Since DHCP clients always request the same IP# they previously had the last
time you should not run into any duplicate IP problems during the
transition. If there are any "hiccups" it should be brief and minor. I have
never had any trouble running ours this way,...our DCs which run DNS, WINS,
and DHCP are identically configured and have done well this way.

 

[Ryan Hanisco]

Marlon,

Phillip is correct. The 50/50 split is just fine if you have one site. If
you are doing this with multiple sites and you put the DHCP local to the
site, the recommended split is 80% of the addresses at the edge and 20% of
the address space at the core.

Just make sure that you have your IP Helper lines in your router configs or
correctly configured VPNs to allow for DHCP requests to traverse your WAN.

--
Ryan Hanisco
MCSE, MCDBA
Flagship Integration Services

You don't need any clusters.

Just configure two DHCP Servers. Configure the DHCP service with exaclty
identical Scopes. The only thing different is that you create and arrange
the Exclusions so that each server gives out one-half of the available
addresses.

If one DHCP dies, you simply remove the extra Exclusion from the remaining
Server so that it can now give out all the available address and it will
keep things going while the other is repaired. When the dead DHCP is
repaired, you just put the Exclusions back the way they were.

Since DHCP clients always request the same IP# they previously had the last
time you should not run into any duplicate IP problems during the
transition. If there are any "hiccups" it should be brief and minor. I have
never had any trouble running ours this way,...our DCs which run DNS, WINS,
and DHCP are identically configured and have done well this way.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

I want to provide failover to DHCP servers.
Is the cluster alternative on Win2003 Ent Server a good way to go ? I have
been reading documentation and I see that MS DHCP is cluster aware, I just
want to know if the cluster solution is practical and works without many
problems.

 

[Marlon Brown]

Currently, my DHCP servers resides on the main office.
Other 20+ offices connect via T1's to get IP addresses from the DHCP
servers.

I still don't understand well how this 20/80 rule works, but I will read the
whitepapers more about it. Basically I need a solution that don't require
manual intervention in case one of the DHCP servers go down.

Marlon,

Phillip is correct. The 50/50 split is just fine if you have one site.
If
you are doing this with multiple sites and you put the DHCP local to the
site, the recommended split is 80% of the addresses at the edge and 20% of
the address space at the core.

Just make sure that you have your IP Helper lines in your router configs
or
correctly configured VPNs to allow for DHCP requests to traverse your WAN.

--
Ryan Hanisco
MCSE, MCDBA
Flagship Integration Services

You don't need any clusters.

Just configure two DHCP Servers. Configure the DHCP service with exaclty
identical Scopes. The only thing different is that you create and
arrange
the Exclusions so that each server gives out one-half of the available
addresses.

If one DHCP dies, you simply remove the extra Exclusion from the
remaining
Server so that it can now give out all the available address and it will
keep things going while the other is repaired. When the dead DHCP is
repaired, you just put the Exclusions back the way they were.

Since DHCP clients always request the same IP# they previously had the last
time you should not run into any duplicate IP problems during the
transition. If there are any "hiccups" it should be brief and minor. I have
never had any trouble running ours this way,...our DCs which run DNS, WINS,
and DHCP are identically configured and have done well this way.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

I want to provide failover to DHCP servers.
Is the cluster alternative on Win2003 Ent Server a good way to go ? I have
been reading documentation and I see that MS DHCP is cluster aware, I just
want to know if the cluster solution is practical and works without
many
problems.

 

[Phillip Windell]

If each office is a different subnet (as it should be), then you'd be best
to have some type of DHCP at each location instead of making the machines
depend on a WAN link [that could go down] to get thier IP# that they
couldn't function without.

It always helps to know the actual design and the situation of a system
before we start answering questions,..it is the difference between a correct
answer and a wrong answer.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com

Currently, my DHCP servers resides on the main office.
Other 20+ offices connect via T1's to get IP addresses from the DHCP
servers.

I still don't understand well how this 20/80 rule works, but I will read the
whitepapers more about it. Basically I need a solution that don't require
manual intervention in case one of the DHCP servers go down.

Marlon,

Phillip is correct. The 50/50 split is just fine if you have one site.
If
you are doing this with multiple sites and you put the DHCP local to the
site, the recommended split is 80% of the addresses at the edge and 20% of
the address space at the core.

Just make sure that you have your IP Helper lines in your router configs
or
correctly configured VPNs to allow for DHCP requests to traverse your WAN.

--
Ryan Hanisco
MCSE, MCDBA
Flagship Integration Services

You don't need any clusters.

Just configure two DHCP Servers. Configure the DHCP service with exaclty
identical Scopes. The only thing different is that you create and
arrange
the Exclusions so that each server gives out one-half of the available
addresses.

If one DHCP dies, you simply remove the extra Exclusion from the
remaining
Server so that it can now give out all the available address and it will
keep things going while the other is repaired. When the dead DHCP is
repaired, you just put the Exclusions back the way they were.

Since DHCP clients always request the same IP# they previously had the last
time you should not run into any duplicate IP problems during the
transition. If there are any "hiccups" it should be brief and minor. I have
never had any trouble running ours this way,...our DCs which run DNS, WINS,
and DHCP are identically configured and have done well this way.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com


I want to provide failover to DHCP servers.
Is the cluster alternative on Win2003 Ent Server a good way to go ? I have
been reading documentation and I see that MS DHCP is cluster aware, I just
want to know if the cluster solution is practical and works without
many
problems.