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Answered DHCP

  • Saturday, May 26, 2012 5:46 AM
     
     
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    I have a scope with IPs assigned addresses from 172.19.1.x using the subnet of 255.255.255.0, and I'm almost out of addresses.

    I'd like to have more IPs assigned as I have more computers coming online in a month.

    Is it best to create a new scope with a subnet of 255.255.0.0 so I can use IPs in the range of 172.19.1.x and 172.19.2.x?

    And if I do create a new scope, will all of the devices with a static IP using the subnet 255.255.255.0 see the new scope?

    Thanks for any help.

     

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  • Saturday, May 26, 2012 8:28 AM
     
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    Hello MS,

    If you are not having any unique reason, what is the use of going to another subnet (255.255.0.0), rather you can use same old subnet (255.255.255.0)

    The only thing you use different IP range (172.16.2.X).

    Regards, Ravikumar P


     
  • Saturday, May 26, 2012 9:50 AM
     
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    Hello,

    Yes, it is best to create a new scope that ranges from 172.19.1.0 to 172.19.2.255 with subnet mask 255.255.0.0, this way all the IPs are in the same subnet, and you will not need any kind of routing or anything. As for the static IPs, you will just have to change the subnet mask to 255.255.0.0 and they will be accessable for all ips.

    P.S. try using DHCP reservation instead of static IPs, this way you can assign static IPs to specific servers, and you can still change other settings like DNS and GW dynamically.

    MCDST, MCSAS, MCSES, MCDBA, MCITP, MCTS, MCT

     
  • Saturday, May 26, 2012 5:47 PM
     
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    By configuring the scope with subnet mask of 255.255.0.0, you must ensure your 172.19.1.x-172.19.2.x clients don't need routing to all 172.19.3.x-172.19.255.x, as all of the clients are in the same class b subnet.

    You need to take care of this.

    Regards, Liran.


    • Edited by Liran.a Saturday, May 26, 2012 5:48 PM
    • Marked As Answer by Tiger LiModerator Friday, June 01, 2012 2:20 AM
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  • Tuesday, May 29, 2012 5:13 AM
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    Hi msenior,

    Thanks for posting here.

    >Is it best to create a new scope with a subnet of 255.255.0.0 so I can use IPs in the range of 172.19.1.x and 172.19.2.x?

    Yes, by either extending address range of scope or adding new scope with super scope and routing settings we can achieve the goal about increasing address space:

    Increasing the number of IP addresses on a subnet in DHCP Server

    http://support.microsoft.com/kb/255999/

    >And if I do create a new scope, will all of the devices with a static IP using the subnet 255.255.255.0 see the new scope?

    May I know how many devices were we set static address for? we’d better to modify network mask for it one by one otherwise they will never see the new address range where is out of the IP segment it can reach (172.19.1.0/24).

    We can also do that in batch by scripting if we do have a lot of hosts that have static address assigned:

    http://gallery.technet.microsoft.com/scriptcenter/site/search?f%5B0%5D.Type=SearchText&f%5B0%5D.Value=mask&f%5B1%5D.Type=RootCategory&f%5B1%5D.Value=networking&f%5B1%5D.Text=Networking

    Thanks.

    Tiger Li

    Tiger Li

    TechNet Community Support


     
  • Tuesday, May 29, 2012 2:22 PM
     
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    In this scenario, the devices that are on the 172.19.1.x/24 will not be able to directly communicate with hosts on the 172.19.2.x/16.  You would need to have a router in between.  This is not an optimal solution based on your description so far.  The best approach would be to configure the hosts on the 172.19.1.x/24 with a /16 network prefix.

    Guides and tutorials, visit ITGeared.com.

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  • Tuesday, May 29, 2012 4:07 PM
     
     
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    Based on a majority of the responses, it sounds like I should remove the current scope and add a superscope to cover the 172.19.1.x and 172.19.2.x ranges with a subnet of 255.255.0.0. Then I'll just need to change the computers/printers with a static IP address.

    I say that because when I added in the 172.19.2.x range (subnet 255.255.255.0) and created a superscope for both ranges, I received an error stating the IP address isn't in the same subnet as the default gateway. This happened when I tried to statically assign 172.16.2.10 to a client.

    • Edited by msenior Tuesday, May 29, 2012 4:38 PM
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  • Wednesday, May 30, 2012 5:39 AM
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    Hi,

    Thanks for update

    > it sounds like I should remove the current scope and add a superscope to cover the 172.19.1.x and 172.19.2.x ranges with a subnet of 255.255.0.0.

    If we decide to use superscope then don’t need to delete current DHCP scope but add a new one with specifying the new address range and creating a new superscope to include both scope in it , after that we need also setting routing in order to make clients that obtain leases form either scope can communicate with each other .Please take look the examples in the KB article below:

     

    Using superscopes
    http://technet.microsoft.com/en-us/library/cc757614(WS.10).aspx

    Thanks.

    Tiger Li

    Tiger Li

    TechNet Community Support

     
  • Wednesday, May 30, 2012 1:06 PM
     
     
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    In the example shown, there needs to be a relay set on the router.  How would the relay be setup?

    I setup a destination network of 172.19.2.1/24 with a default gateway of 172.19.1.1.  Is that correct?

     
  • Wednesday, May 30, 2012 3:00 PM
     
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    I would not recommend the superscope as the best design.  I would schedule this implementation during a maintenance period.  

    Option 1) Delete the existing scopes, create a new scope for 172.19.x.x/16, and update the subnet mask on your hosts that have static configurations.  In your DHCP scope, make sure that conflict detection is enabled.  restart the dhcp clients (or just issue ipconfig /rewnew from the command prompt) and within the hour, all conflicts should be cleared from your scope and you'll have all network clients on the same subnet without any additional router configuration, or relay agents.

    Option 2) Create a new VLAN for 172.19.2.x/24 on your network equipment.  Add new devices to this new segment.  Add the relay agent for that segment (on the router), create a new scope in DHCP to service 172.19.2.x/24.

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