DHCP Fight...

Cyber Dude

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Jul 13, 2005, 8:25:42 PM7/13/05

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Hi,

had a visitor at one of my customers the other day...his XP laptop was
configured for home networking (therefore distributing IPs) and knocked
the DHCP server down in no time at all...

How do I prevent this from happening besides not allowing this type of
visitor?

Thanks,
Cyber Dude

Merv Porter [SBS-MVP]

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Jul 13, 2005, 10:11:50 PM7/13/05

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Install 2 NICs/router on your network and then connect any "visitors"
directly to a port on the router (which will be outside your LAN and not
affect the SBS server). If you need to give the "visitors" wireless
Internet access, connect a Wireless Access Point (WAP) to a port on the
router (again, this will be outside your LAN). You really don't want to
give LAN access to an unknown/untrusted device (laptop, PDA, Tablet PC,
etc.).

--
Merv Porter [SBS MVP]
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"Cyber Dude" <cyber...@yahoo.com.br> wrote in message
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Russ Grover

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Jul 13, 2005, 11:14:39 PM7/13/05

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A Laptop to Distribute IP's? Now there's something I've never thought of
Laugh!
(I'd hate to see his network layout) Laugh!

--
Russ Grover
Small Business IT Support
Portland\Beaverton OR USA
Email: Sales at SmallBusinessITSupport.com
Website: www.SmallBusinessITSupport.com

"Cyber Dude" <cyber...@yahoo.com.br> wrote in message
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Lanwench [MVP - Exchange]

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Jul 14, 2005, 12:25:02 AM7/14/05

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In news:Or6duICi...@tk2msftngp13.phx.gbl,
Russ Grover <russ@NOSPAM_SmallBusinessITSupportDOTcom> typed:

> A Laptop to Distribute IP's? Now there's something I've never thought
> of Laugh!
> (I'd hate to see his network layout) Laugh!

Please google for ICS. :)

Lanwench [MVP - Exchange]

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Jul 14, 2005, 12:26:34 AM7/14/05

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In news:uXSvSqAi...@TK2MSFTNGP12.phx.gbl,
Cyber Dude <cyber...@yahoo.com.br> typed:

Smack anyone who even tries to plug in an unauthorized computer (and don't
leave any network drops connected live to the hub/switch when not in use by
a legit computer). Leave welts as a warning to others.

Rogue DHCP servers are the least of your worries.

>
> Thanks,
> Cyber Dude

Russ Grover

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Jul 14, 2005, 2:00:46 AM7/14/05

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Yes but using the laptop as the ICS?

--
Russ Grover
Small Business IT Support
Portland\Beaverton OR USA
Email: Sales at SmallBusinessITSupport.com
Website: www.SmallBusinessITSupport.com

"Lanwench [MVP - Exchange]"
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Charles Yang [MSFT]

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Jul 14, 2005, 4:13:28 AM7/14/05

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Hi Cyber,

Thanks for using this newsgroup.

Problem description:

I understand that you have a visitor whose laptop host DHCP services when
he entered into SBS domain, DHCP services on SBS is down.

Analyzing and suggestions:

By default, SBS 2003 will disable its DHCP server if it detects another
DHCP server on the network. This behavior is by design. The recommended
solution is to use only one DHCP server on the network.

You can try the Merv's workaround to attach the laptop on the same subnet
of SBS external NIC and use a router to access the internet, this will not
impact the SBS internal domain, however there might be some problem to
access the internal resources directly.

We also have a solution to allow the SBS domain host more than one DHCP
server on the same domain. You can disable rogue detection by creating the
following registry entry:

Navigate to
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Dhcpserver\Parameters

On the Edit menu, click New->DWORD Value, and then add the following
registry value:

Value name: DisableRogueDetection
Data type: REG_DWORD
Radix: Binary
Value data: (Hexadecimal) 1, which will be saved as 0x00000001

Restart the server.

Please note that if you have multiple DHCP servers, the scope on each
server should not have the same range of overlapping addresses. For
instance, one server should have an available range of 192.168.16.1 to
192.168.16.128 and the second server should have an available range of
192.168.16.129 to 192.168.16.254 if the network mask is 24 bit
(255.255.255.0).

I appreciate your understanding on this issue, if you have any further
concerns, please let me know. I am glad to be any further assistance.

Best regards,

Charles Yang (MSFT)

Microsoft CSS Online Newsgroup Support

Get Secure! - www.microsoft.com/security

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Cyber Dude

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Jul 14, 2005, 6:00:10 PM7/14/05

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Cyber Dude wrote:

thanks to all for your valuable inputs...
however, I'm still flaberghasted at how a DHCP server on a DOMAIN would
shut it itself to a WS with ICS enabled....that's ridi-culo-us to me...

why doesn't M$ throw a little feature for when something like this comes
up, the DHCP server has prevailing existing (breathing) rights over a WS?

All the other solutions are quite obvious to me, but because of strapped
$$ resources, that's the way it's setup right now...

many thanks to all,
Cyber Dude

Message has been deleted

Charles Yang [MSFT]

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Jul 15, 2005, 1:25:59 AM7/15/05

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HI,

Thanks all for good sharing, hope you can find your solution. It seems this
issue might be the by design issue in SBS domain. We do not recommend to
add another DHCP server on SBS domain.

You can add a NAT router to external NIC of SBS then connect to this client.
You can also set up the DHCP services on SBS to avoid the interruption with
your visitor.
Temporally stop the DHCP services on visitor and join the domain.

I appreciate your understanding on this issue.