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DHCP assigned metrics with Windows 7 clients

Posted on 2011-03-09
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Last Modified: 2012-05-11
I have 100 Windows 7 laptops that, when docked, have an active wired and wireless connection at the same time.  Our Windows Server 2008 R2 AD server issues DHCP addresses on a different subnet for for wired connections versus wireless connections.

I'm trying to configure a Metric for the wireless DHCP addresses using the scope option of "Microsoft Default Router Metric Base" and assigning a value of 0x1F4 (or 500 in decimal).  This is to ensure that when laptops are docked with active wired and wireless connections that the wired connection will take priority.  However, the scope option doesn't seem to be taking effect on the wireless adapter settings.  

After renewing the DHCP addresses, running "ROUTE PRINT" on the laptop shows that the wired metric is 266 and the wireless is 276 - just as before.  All other scope options are fine (router, gateways, etc.).

Manually changing the adapter and bindings settings on each laptop by moving the "Local Area Connection" to the top of the list is not feasible in this situation.

Any ideas?
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Question by:curt2000
9 Comments
 
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Expert Comment

by:Raheman M. Abdul
Comment Utility
Go to System, device manager, select your LAN network adapter, properties, and in advanced, you should find the of options u are looking for

Try the options to see if it helps.
(refer: http://www.tomshardware.co.uk/forum/31846-17-select-wireless-internet-wired-internet ) for some guidance
See the image at the end of the document
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Author Comment

by:curt2000
Comment Utility
For the particular laptop I'm on now the wireless adapter does not have the option for enabling Priority or VLAN.  The wired adapter does, but I'm trying to set a metric for the wireless adapter via DHCP.
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Accepted Solution

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MarkieS earned 500 total points
Comment Utility
If you can run a VBS script on each laptop as it logs in this works beautifully...
http://support.microsoft.com/kb/894564

'  
'  Script is to change Metrics of TCP connections so that Local Area Connections are preferred for
'  TCP/IP traffic and Wireless connections are least preferred
'
'

On Error Resume Next

strComputer = "."
Set objWMIService = GetObject("winmgmts:" & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")

regValueDataMetric = "35"

Set colItems = objWMIService.ExecQuery _
("Select * From Win32_NetworkAdapter Where NetConnectionID = 'Wireless Network Connection'")

For Each objItem in colItems
strMACAddress = objItem.MACAddress
'   Wscript.Echo "MACAddress: " & strMACAddress
Next

Set colNetCard = objWMIService.ExecQuery ("Select * From Win32_NetworkAdapterConfiguration where IPEnabled=TRUE")

For Each objNetCard in colNetCard
If objNetCard.MACAddress = strMACAddress Then
For Each strIPAddress in objNetCard.IPAddress
'   Wscript.Echo "Description: " & objNetCard.Description
'   Wscript.Echo "IP Address: " & strIPAddress
'   Wscript.Echo "IPConnectionMetric: " & objNetCard.IPConnectionMetric
objNetCard.SetIPConnectionMetric(regValueDataMetric)
Next
End If
Next



regValueDataMetric = "1"

Set colItems = objWMIService.ExecQuery ("Select * From Win32_NetworkAdapter Where NetConnectionID = 'Local Area Connection'")

For Each objItem in colItems
strMACAddress = objItem.MACAddress
'   Wscript.Echo "MACAddress: " & strMACAddress
Next

Set colNetCard = objWMIService.ExecQuery ("Select * From Win32_NetworkAdapterConfiguration where IPEnabled=TRUE")

For Each objNetCard in colNetCard
If objNetCard.MACAddress = strMACAddress Then
For Each strIPAddress in objNetCard.IPAddress
'   Wscript.Echo "Description: " & objNetCard.Description
'   Wscript.Echo "IP Address: " & strIPAddress
'   Wscript.Echo "IPConnectionMetric: " & objNetCard.IPConnectionMetric
objNetCard.SetIPConnectionMetric(regValueDataMetric)
Next
End If
Next
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Expert Comment

by:vivigatt
Comment Utility
Check this page:
http://technet.microsoft.com/en-us/library/cc782411%28WS.10%29.aspx

It says:

-------
Default Router Metric Base

This option can be used to set the default base metric for DHCP clients running Windows Server 2003. When this option is set, the DHCP Client service uses the value configured here as the base metric for its default gateways.
Code

3
Length

4 octets
Value

This value represents a specified router metric base to be used for all default gateway routes used by DHCP-enabled clients running Windows Server 2003. This value can be assigned as an integer representing a cost metric ranging from 1 through 9,999. It is used in calculating the fastest, most reliable, and least expensive routes. If a value is not specified, a default of either one (1) or the currently set interface-specific metric is used.

---------

If it works with WIn2003 clients, it might also work with Win7 clients.
Its in "microsoft options":


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Expert Comment

by:vivigatt
Comment Utility
Sorry, I pressed OK before being done !
I was saying, it is in "Microsoft Options":

 Bb878031.cg040501-l-en-us-.gif

You get there this way:
DHCP/Server Options or Scope Options (or even options in reservations)
Advanced Tab
Select "Microsoft Options".

Tell us if this worked !

HTH
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Author Comment

by:curt2000
Comment Utility
Sorry for the delay in responses, I was in meetings all day yesterday.

MarkieS - Thanks for the script.  I'll have to try it out, but looks like it could work in our environment.  Previously I found another person that was using a script for their solution too (found at http://www.myitforum.com/forums/m173977.aspx), but I was hoping I could accomplish my task by using a DHCP scope option.  I'll try out your script and it's much appreciated.

vivigatt - Thanks for the info too, but that was the solution I started with before posting my question.  I haven't been able to get it to work.  Again, I used 0x1F4 for my metric base, but it doesn't seem to impact my Windows 7 machines.  Do you think that this applies to only Windows XP and older clients maybe?  I'll have to test this just to find out.
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Expert Comment

by:vivigatt
Comment Utility
The metric assigned by DHCP is only for the route to the default gateway. But I admit that I never tried to use it... I'll try that later and if I understand how it works/what it does, I'll tell you

If you want you can read my article:
http://www.experts-exchange.com/Software/System_Utilities/Remote_Access/VPN/A_2977-VPN-use-default-gateway-AND-access-your-local-network.html

With my NICIndex utility, you can use
route change
to change the metric of a specific route.
A script run on the client side then becomes as simple as:

 
NICIndex.exe /IPPrefix=193.105.13. /Type=Ethernet > %temp%\SetNIC.bat
if exist %temp%\SetNIC.bat call %temp%\SetNIC.bat
route change 192.105.13.0 MASK 255.255.255.0 %NICIP% Metric 50 IF %NICIDX%

Open in new window


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Author Closing Comment

by:curt2000
Comment Utility
This is the solution that worked for us.  Thanks for sharing!
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Author Comment

by:curt2000
Comment Utility
Oops, I should state the script from MarkieS is the solution.
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