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Enabling DHCP Server on SBS 2008: Plus's and minus's

Posted on 2012-03-18
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Please note this Question is **NOT** about a production environment. It is about a training/learning environment I am using to go thru a MS Press textbook to get my SBS 2008 MS Certification. Hence phrases like "best practices" are irrelevant.

Also although I know a great deal about the MS "home" OS's (If fix PCs for a living), I know NOTHING about SBS 2008 except how to install it and answer some required installation questions so please spell your answers out in detail. Do NOT assume I know the basics, I do NOT know the basics (yet).

QUESTION: What are the plus's and minus's (especially the minus's) of NOT enabling DHCP server on the SBS 2008 PC.

My entire network is ONE client PC connected to a router (connected to a Comcast modem) and a SBS 2008 PC (used as a server) connected to the same router PLUS a roommates PC connected wirelessly to the same router.

My concern in enabling DHCP server on SBS 2008 is that decision impacts my business PC and my roommates PC. Example. My ISP has an outage that it later recovers from. In my experience I often need to powercycle BOTH the modem and the router to recover after the outage is over. If the SBS 2008 PC is the DHCP server **HOW** do I use it to reassign the ip addresses. I mean please provide a fairly detailed step by step answer for two cases below.

Also I believe (but am not sure) that the ip addresses are on "lease" and must be anto-renewed every 24 hours. Will that require case (B) below (always leaving the SBS 2008 PC on) as the always-on router will no longer be doing that.

(A) My SBS 2008 PC is ONLY on when I want to move thru the text book and learn more. i.e it is usually off (example during the ISP outage and recovery).

(B) My SBS 2008 PC is ALWAYS on except for reboots for updates and occasional other needs.

I am listing (B) as I would not be surprised if you answer that making the SBS 2008 PC the DHCP server is not very practical unless the server is ALWAYS on (or close).

Regards,
  Mike
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Question by:mgross333
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by:Larry Struckmeyer MVP
Larry Struckmeyer MVP earned 200 total points
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You have it right.  If the SBS server is not turned on you must enable DHCP on the router.

In a production environment the servers are "always" on, and therefore it makes sense for them to be the DHCP server as they pass some variables to the clients that only make sense in a domain/SBS network.

Since you are studying this subject I suggest you go for SBS 2011 as that is the current cert and will gain you the Small Business Specialist certification.  In the process you can search the net for the parameters the SBS DHCP server passes to the clients.

Good luck on your quest.
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by:Rob Williams
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Probably the best article on the subject:
"Do I absolutely have to run DHCP on SBS 2008?"
http://sbs.seandaniel.com/2008/10/do-i-absolutely-have-to-run-dhcp-on-sbs.html
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Cliff Galiher earned 150 total points
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Unfortunately you are in a unique catch-22. Because your server is mostly off, DHCP SHOULD be on the router, and the router should pass out ISP DNS servers. But in so doing, you break your SBS setup for any SBS client computers; a very necessary part of learning SBS.

In short, you've created a fundamentally broken test environment. I'd encourage you to reconsider a deployments on either an isolated network, or at the very least a virtualized environment so you can run a setup as designed, with DHCP (and DNS) on SBS, but where SBS being off won't affect your production environment in any way.

I went into much greater detail in answering your other question, but the principle holds true here as wel
.

-Cliff
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by:KCTS
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With a windows based domain  - and SBS is a domain, one of the critical things is that all the servers and all of the clients MUST use ONLY the windows server as their DNS server, and this is configured in DHCP.

SBS based DHCP can be (and should be) set so that it gives all clients the SBS server as the DNS server.

One problem with router based DHCP is that is often sets clients to use the router itself as the DNS server and with many routers you cannot change this. If this is the case then internal DNS name resolution (and by implication) your domain will fail.
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by:mgross333
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THANKS to all for your replies. Please reply to (2)below (end of this post) that I asked about above but have received no replies on. Also please reply to (3) below that is essentially related.

(1) fl_flyfishing

Regarding "...I suggest you go for SBS 2011 ...", it is my understanding that most small business sites are still running SBS 2008 and hence that knowledge will be most valuable in getting short -term contract work that require SBS 2008 expertise. (I also plan to continue my PC fixit and upgrde (including networks) business that I have been doing for 7 years)

RobWill

Thanks for the link however that links shows no pressing reason I should enable DHCP server to go thru my training materials. However the posts here ALREADY provide reasons I SHOULD enable DHCP (as well as DNS server).

cgaliher

Thanks for your comments here as well as your more detailed comments at

http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/Windows_Server_2008/Q_27637691.html

However regarding "Because your server is mostly off, ", as I replied to you at the link immediately above that is NOT decided yet. I am using the replies here and at the link above to decide on that.

(2) I asked in the EE question you are replying to the following question whose answer is needed if I am to enable DHCP server on the SBS 2008 PC.

Assume below that the SBS 2008 PC is ALWAYS ON (except when I need to restart to install SBS 2008 updates or for other very occasional reasons)

"My ISP has an outage that it later recovers from. In my experience I often need to powercycle BOTH the modem and the router to recover after the outage is over. If the SBS 2008 PC is the DHCP server **HOW** do I use it to reassign the ip addresses."

i.e Do I need to go to the SBS 2008 PC and enter some commands EXPLICITLY. If so please list what I need to do in some detail.
OR
do I need to powercycle the SBS 2008 PC
OR
do nothing,. the SBS 2008 PC will take care of it
OR
something else.

(3) My SBS 2008 PC is dual boot (Windows 7 and SBS 2008). I will ALSO (in addition to what is said above) occasionally need to boot it to Windows 7 to solve a customer Windows 7 (or Vista as the interface is similar) problem where I need to try something or see something to understand a customer question NOTING that my business PC is Windows XP SP3. This is rare as I already work with Windows 7 and Vista quite a bit BUT occasionally something comes up that I have not worked on.

That situation could last up to an hour.


My question is assuming that the SBS 2008 PC is the DHCP server and DNS server what is the impact on my business PC and my roomates PC.

I am hoping the answer is NONE. Because ip addresses are already assigned and the router still works (although it is not the DHCP server). An exception may be when a DHCP lease expires but the chance that will happen during the hour I am running the SBS 2008 PC as a Windows 7 PC is small.

As for translating URLs to ip addresses (ie the job of DNS) I am **HOPING** that when SBS 2008 is NOT running, DNS will AUTOMATICALLY go back to ISP DNS via the router. So there will be no impact. However I am hardly sure about this 2nd point !!

I hope you understand the issue here. I have a rooomate who expects internet services as part of his rent. If they will be interrupted when the SBS PC is booted to Windows 7 I have to let him know that. I also sometimes need both internet use of my XP SP3 Office PC and the Windows 7 PC at the same time.

Regards-Mike
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by:Larry Struckmeyer MVP
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Speed reading through your post so I may not be answering all the questions, but in regards to DNS failover:  Yes, if you have BOTH the SBS DNS and the ISP DNS settings in your clients and the query cannot be resolved by the SBS because it does not answer and therefore cannot give forwarders or root hints, your client will failover to the ISP DNS server.

What is not stated in your question is how to revert to the SBS DNS, and the answer is:  You can't.  Only turning the client off, the SBS on, then the client back on will do that.  DNS failover is not a first choice then second choice.  It is:  First Choice until there is no First Choice, thereafter Second Choice.
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by:Cliff Galiher
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There are two distinct problems with your plan.

First, your dual boot scenario means that your SBS server will be gone when you boot up win7. By propy, your DHCP server will be gone. Your win7 machine will have to be assigned a static IP because it will never be on at the same time as the DHCP server.

The second problem is much harder to get past. For AD to work properly, ALL DNS servers should be AD servers. That means that when SBS is off,munoessmyouve set up a second AD DNS server, your DNS server is also off. It will NOT revert to ISP DNS servers. While you can technically configure ISP DNS servers as secondary servers on the client, doing so has known adverse effects on AD, which means while SBS is on, your clients will not work as expected or as documented in any AD books or technet articles. Mixing AD and non-AD DNS servers is universally considered VERY VERY BAD. So yes, turning off the SBS server will cause problems on your network.

Which brings me back to my previous suggestion. The onky way to safely do what you want is to isolate the test network. With virtualization, this is very easy to do. Nearly trivial. As you start learnini new products and want to test changes, this will become increasingly useful.

-Cliff
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by:Rob Williams
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It really comes down to are you wanting to play, or learn how to properly implement and manage an SBS server.
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by:mgross333
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Thanks again for all the replies.

First things first

Rob Will, Regarding"are you wanting to play, or learn how to properly implement and manage an SBS server."

My goal is to ONLY get the MS Certification to put on my resume to get contract work . The contract work (to be added to income from my business) is NOT 100% or even primarily Windows server oriented or full time. Some people who I trust have told me if I have the server certification on my resume they **CAN** get me contract work given the rest of my background.

Hence "learn how to properly implement and manage an SBS server" is a bit beyond my goal.

Now to address the specifics in the current round of replies. First booting the dual boot PC to Windows 7 is only one example of what I want. I would prefer to get out of the SBS 2008 environment occasionally and use my and my roommates PC in the current arrangement. The Windows 7 case  is really a 3rd PC connected to the router in the current non-SBS managed environment

fl_flyfishing seems to say "no problem" as long as I am willing to " turning the client off, the SBS on, then the client back on will do that". (ie to set up the SBS 2008 environment again).

However cgaliher points out a problem : "your SBS server will be gone when you boot up win7. By propy, your DHCP server will be gone. Your win7 machine will have to be assigned a static IP".

My solution to that is to go into the Linksys router admin utility (my office PC is wired to it) and turn the DHCP service on again and reboot modem, router and (if necessary) all relevant PCs. Then before going back to the SBS 2008 environment disable DHCP server in the router etc etc

However then cgaliher points out a more serious problem. "....Mixing AD and non-AD DNS servers is universally considered VERY VERY BAD. So yes, turning off the SBS server will cause problems on your network." (Non-AD will occur when I leave the SBS 2008 environment).

Two solutions: One is a virtual environment which I will now be discussing further with
cgaliher  at

http://www.experts-exchange.com/OS/Microsoft_Operating_Systems/Server/Windows_Server_2008/Q_27637691.html

Solution 2: Suggested by CrisHanna_MVP of the EE forum is essentially THIS

Connect two more routers to the LAN outputs of my current Linksys router. Connect my PC and the SBS 2008 PC (wired) to Router one and make the SBS 2008 PC the DHCP and DNS server. And connect my roommates laptop wirelessly to the other router, router 2. Then when I want to switch between the SBS 2008 and non-SBS 2008 environment just disconnect the ethernet cables from the SBS server and my PC from Router 1 and connect them to router 2 and power cycle modem and Router 2. ie. isolate the SBS 2008 stuff to router 1.

QUESTION: Will this idea solve ALL the problems mentioned above?

Mike
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by:Cliff Galiher
Cliff Galiher earned 150 total points
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It will, in theory (and with much configuration) solve all of the problems I raised. It does, however, raise one potential concern. By daisy chaining routers, your traffic will be going through not one, but two NAT translations. In most cases this is a no -issue, but some applications (yahoo messenger was one last I checked) don't play well when translated more than once. If you or your roommate use an Internet application that disagrees with a multi-NAT topology, that application will cease to function with your plan.

-Cliff
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by:Larry Struckmeyer MVP
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Remind us again why you don't just leave the SBS turned on and allow the stations, domain joined or not, to get their IP and DNS assignements from their?  If it is to save electricty when not using it, at that point turn on DHCP on the router.  Expecially if your station is the only one to be domain joined and you choose to dual boot to the non domain instance on that system when the SBS is off and the router's DHCP is on.
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by:Rob Williams
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Isolating the two networks will work fine for outgoing services, but if you wish to tinker with incoming services such as VPN, as Cliff says, they will not support dual NATing.  If interested you can configure as per option 2 or 3 in the following link
http://blog.lan-tech.ca/2011/05/23/create-an-isolated-network-using-one-isp-connection-and-modem/

I would have to add these two comments are somewhat in contradiction to one another:
"My goal is to ONLY get the MS Certification to put on my resume to get contract work .............learn how to properly implement and manage an SBS server" is a bit beyond my goal."
Far too often we see people getting a certification one way or another with no interest in learning how to properly manage the equipment and hardware they were hired to maintain. Long term it is well worth your while to gain a thorough knowledge of the server products.
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by:mgross333
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fl_flyfishing

Regarding "Remind us again why you don't just leave the SBS turned on and allow the stations, domain joined or not, to get their IP and DNS assignements from their?  If it is to save electricty ..."

It is because I may make a mistake in setting up or configuring SBS at some point in going thru my MS certification guide and that will cause my office PC or my roommates PC to loose internet. It has nothing to do with the electric bill; I would be quite happy to leave my new SBS PC on 24/7 if there were not the above issue.

RobWill (1st paragraph latest post) and cgaliher

#1 RobWill. First THANK you for the excellent link.

The only use of VPN will be from client PCs on the local LAN, not from any PCs outside the modem.  

# 2 cgaliher I use NO messaging app (yahoo messenger or AIM or any of them). I will ask my roommate if he uses them.

As for remote desktop, again I do not think I or my roommate need that . The main use of that is to have Dell or HP or Microsoft etc take over a PC and solve a problem. As solving desktop PC problems is WHAT I do for a living, that service is not needed for me and I do this for my roommate for free as he is my roommate.

RobWill (2nd paragraph) People do not ask me to know EVERYTHING about a subject. They pay me to solve ONE PARTICULAR problem. Now some people need to know a lot about a subject (in this case SBS)  to do even one problem. I do not; I am very good at finding how to solve problems with LIMITED knowledge. If I could not do that I would not be in business for 7 years as I knew very little about PCs or MACs when I started my business. I learn bit by bit. I learn ON THE JOB.

Now after two years of solving INDIVIDUAL SBS problems, I will probably know enough to as you put it "how to properly implement and manage an SBS server". But not at the start. My goal is to get individual short term jobs involving SBS . Two people who know me well say I can do that if I simply get ONE SBS certification on my resume (in this case for SBS 2008) so that some customers will hire me.

Mike
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by:Larry Struckmeyer MVP
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In the below case, you simply turn off the SBS and turn DHCP On on the router.  You cannot cover every possible case with one setup, certainly not if you wish to call it "normal".  If the SBS is off the router's services must be on.  If the router's services are off they must be ON somewhere, in this case the SBS.

"It is because I may make a mistake in setting up or configuring SBS at some point in going thru my MS certification guide and that will cause my office PC or my roommates PC to loose internet. It has nothing to do with the electric bill; I would be quite happy to leave my new SBS PC on 24/7 if there were not the above issue."
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by:mgross333
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I selected cgaliher as the best solution because he suggest running SBS 2008 in a virtual environment to avoid the problems with turning on DNS and DHCP server in SBS 2008. I also appreciate that he as he was the first one to point out the incoming app problem with the daisy chained router solution. (RobWill then provided more detail on the incoming app problem). However all the other posts awarded points here provided useful info on why I **MUST** turn on DNS and DHCP server in SBS.
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