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DHCP setup on wired and wireless

Posted on 2016-09-13
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Last Modified: 2016-09-29
This may be very basic for some people.

i have a home network. Windows Essentials. Five different servers, one of which is the domain controller with DHCP running. The reserved range is 192.168.0.1 to 19. So from 192.168.25.20 to .255 is available.

I have a LTE Router 192.168.25.1 and that is all fine.

From the router I set up a wireless SSID. I use it to connect my 2 notebooks and 2 smartphones. So I have to give it an IP. To do this I have to switch the DHCP of the router on. I set the range 200 to 255.

I then get an IP on my PC's in the 2xx range and I can't access my network forders and applications across the domain. It wants me to log in every time. But I have already logged in. If I switch the DHCP on the router off, everything works except the wireless.

How do I fix this.
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Question by:alexangus
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LVL 16
ID: 41796247
What exactly are you trying to accomplish having two different devices performing DHCP? I'm confused about that part. Also, you indicated the reserved range for DHCP from your server is 192.168.0.1  to 19, and then mentioned that the rest of the available range is 192.168.25.20 to .255 (I assume you meant .254 as the last usable IP). What's going on with these two difference network segments? Is it .0.X or .25.X?

You should only have DHCP running on one device. There are reasons to have more than one, but those don't really apply to your home network.

MO
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by:Russ Suter
ID: 41796270
You should check your subnet mask. Most likely it is 255.255.255.0 which means no device with an IP address beginning with 192.168.0.xxx will be able to talk to any device with an IP of 192.168.25.xxx.

You have 3 options:

1. Homogenize your network so all IP addresses begin with the same 3 octets. (i.e. make them all 192.168.0.xxx or 192.168.25.xxx)
2. Alter your subnet mask so it's 255.255.0.0. This is perfectly legit to do. It's just not done very often.
3. Create a routing table to allow traffic between two different subnets. You really don't wanna go here unless you have a very good reason. It gets tricky to implement properly and offers no real benefit in a home environment.

If I were you I'd probably go with option 2. It's by far the easiest.
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by:pony10us
ID: 41796385
@Russ

"2. Alter your subnet mask so it's 255.255.0.0. This is perfectly legit to do. It's just not done very often."

Wouldn't you want to tighten this down a little and use 255.255.224.0?  This would restrict the network to 192.168.0.xxx - 192.168.31.xxx.  Still a large network though.

Just a thought.  :)
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LVL 16
ID: 41796454
Ummm, is it just me that thinks it's odd that there are 2 different Class C segments for the authors home and if there doesn't need to be why are there two different DHCP servers.

How about just consolidating to a single Class C subnet? @Russ, that was your original suggestion item number 1 and is what I agree with doing. Subnetting with a Class B mask either /16 or /18 (as indicated by pony10us) just seems a bit much for a home network. A broadcast space of 8000+ (/18) or 65000+ (/16) host addresses just is not good practice unless you have a good reason. I can't see that reason in this particular home network.

MO
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by:Russ Suter
ID: 41796465
@pony10us

Sure, you could restrict the subnet a bit further but this is a home network. How much does that really matter?

@Michael Ortega

Consolidating the subnet would be accomplished by either suggestion 1 or 2. Again, it's a home network. I try not to put too much thought into it. IMHO option 2 is the fastest fix.
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LVL 16
ID: 41796479
@Russ,

I completely understand. I guess I'm overly critical about this kind of thing and generally approach everything from a best practice perspective. Plus, I generally like to know why someone does something a certain way when it seems unusual, e.g. 2 subnets in a home.

MO
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Author Comment

by:alexangus
ID: 41796584
Firstly, my humble apologies. Its not 192.168.0.1 to 19, its 192.168.25.1 to 19.
Very sorry about that. And embarrasing for not checking before I posted.

Well I am no expert which is why I come to the experts. Accounting, that is my world.
Yes it is a home network. Let me give you the long story to explain my problem and lack of knowledge.

I have 5 servers because one is the DC and the other 4, soon to be 5, each has a different OS (either 2008 or 2012) and a different SQL (2005, 2008, 2012 and 2014) and the last 4 versions of the accounting software I support. If I had one big server I could make VM's but I have cheap HP Micro Servers with lots of HDD space. So when a client calls and he has a system 2 versions back, I will have a copy of his configuration loaded on a server that I can just quickly connect to via RDP, sort his problem, write a report and so on. The servers are 192.168.25.10, 192.168.25.11 and so on up to 192.168.25.14. The ADSL router is 192.168.25.1. The printers are 192.168.25.21 and .22 (2 printers).

I do not have any 192.168.0.x around. Not as part of this network anyway.
I have just signed up for an LTE router to get more speed because ADSL 6Mb is too slow and FTTH is some years off in my area. I can sometimes be connected to 4 clients at the same time. That is my basic setup and about as much as my brain can handle. Sorry, at 68 I try my best. I did configure all this myself, so know enough to be dangerous as they say.

Now I want to activate the wireless on the router so I can use the cheaper bandwidth for internet access. I also have a notebook that I use for Work. So I want to log onto the domain, access printers and applications and move data back and forwards. So my notebook login is as a domain user. Mainly I use cable on the Dell XPS notebook because I can boot in 1 min, print something or get a file and I run to the next client.

Sometimes I am doing training and want to connect from another room via wireless. No cable there. I also want to connect my smartphone. So here I hit a problem. How do I configure the wireless side so I can pick up the correct connection. I assume this has to be a 192.168.25.x IP address? The DC can't (not that I am ware of) issue an IP address via the wireless network.

I understand that I can't have two DHCP's on the same subnet (hope my terminology is correct). I know this has to work, but how to do it?

Once again, sorry for misleading you on the 192.168.0.x typo. I hope I have checked all the facts this time.
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Accepted Solution

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pony10us earned 500 total points
ID: 41796694
Let's see about diagraming this out.

Internet --->  ADSL (192.168.25.1)
ADSL ---> switch?
switch ---> 2 printers and 5 servers

DC also acts as DHCP server

Couple of thoughts.

1. With only 2 printers and 5 servers why not use hard coded IP addresses instead of DHCP. Then you can use DHCP from the ADSL for the wireless and exclude the hardcoded addresses.

2. Don't turn on the wireless on the ADSL and instead add a separate wireless model as an AP?  Not to advertise for any specific brand but there is a good set of instructions for this option using a DLink.

http://www.binarytides.com/wireless-router-existing-wired-network-lan/
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Expert Comment

by:Fred Marshall
ID: 41796910
I understand the diagram as follows:

Internet modem which maybe includes a router but I'll assume that this is transparent even if there's NAT.
LTE Router with NAT and with wireless running DHCP.
Various hosts including a DC running DHCP.

You might productively split the DHCP range into 1) wired from DC and 2) wireless from router.
This isn't good practice but it should work in a case like this.
If you're going to do this, it might be a good idea to reserve the wireless IP addresses for known devices (by MAC address) in the router setup - and keep them out of the DC DHCP range.
If this doesn't meet your DC functionality then it may not be suitable.

The other way to do this is to add a wireless router or access point to the LAN and let the DC do *all* the DHCP.  A diagram is attached for doing this with a commodity router: "Wireless Router as Access Point"
Wireless-Router-as-a-Simple-Switch-a.pdf
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Author Closing Comment

by:alexangus
ID: 41821940
Seems to work so far.
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