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single dhcp server, 2 subnet masks?

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single dhcp server, 2 subnet masks?

kjrees
Hi, I wondered if it was possible to set up a single windows server 2003 dhcp server to lease addresses to clients from two seperate networks that have different subnet masks?
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    markp24

    Hi here is an article on how to do multiple subnets from a dhcp server

    http://technet.microsoft.com/en-us/library/cc758865(WS.10).aspx

    hope this helps

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    kjrees

    thanks for the reply....it's not quite what i'm asking. I know that you can use a single dhcp server to serve multiple subnets, but i'm asking that if the subnet mask was different on the second network could the dhcp server serve both?

    i have doubts that it would work as i that would make them on different networks, but the two networks can communicate with static routes set up between them on a layer 3 switch, so i've been asked to investigate if a dhcp server on the first network could be used. network one has a mask of 255.255.248.0 and network two has a mask of 255.255.255.0.

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    markp24

    Hi, I do believe you need a DHCP relay server in order for that to work. Ill see i can fin of a working example of this type of setup.

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    Layer 3 is handling the routing so you can define whatever subnet mask is required for the networks via DHCP

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    frank.williams

    If your switches cannot pass through DHCP/BOOTP packets then it is likely you would need a DHCP relay server in the 2nd subnet set up with 2 network adapters. 1 adapter configured for subnet 1 to allow the relay to chat back with the main DHCP server and another adapter configured for the 2nd subnet to allow DHCP messages to be 'relayed' to devices on that particular subnet.

    I think that is correct but it's been a little while since I configured anything like that ;-)

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    And if your Switches are layer 3 as indicated they should be able to pass DHCP/BOOTP packets with a helper address of the DHCP Server on each Layer 3 interface/subnet that the DHCP Server does not sit on

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    kjrees

    i think Markp24's example is when the subnet masks are all the same in each subnet. If you try and set up different scopes with different subnet masks then DHCP says:

    "the scope parameters are incorrect. Either the scope already exists or it's subnet address and mask is inconsistent with the subnet address and mask of an existing scope."

    basically in my example, there is a primary LAN with a mask of 255.255.248.0 and on a separate vlan the network has been configured with a mask of 255.255.255.0, but the vlan doesn't have a dhcp server. I think that in order for the Vlan's clients to use DHCP from the primary LAN, both the VLAN network and the primary LAN should have the same subnet mask or it won't work?

    in terms of connectivity, the primary LAN and the VLAN can communicate with eachother (ping) via static routes set up on the layer3 switch connected to the VLAN and also in RRAS on the ISA server machine direclty connected to the primary LAN.

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    kjrees

    i'm thinking maybe a superscope might be the way to go(?)

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    1 Votes
    markp24

    Hi here is an article on how to do multiple subnets from a dhcp server

    http://technet.microsoft.com/en-us/library/cc758865(WS.10).aspx

    hope this helps

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    0 Votes
    kjrees

    thanks for the reply....it's not quite what i'm asking. I know that you can use a single dhcp server to serve multiple subnets, but i'm asking that if the subnet mask was different on the second network could the dhcp server serve both?

    i have doubts that it would work as i that would make them on different networks, but the two networks can communicate with static routes set up between them on a layer 3 switch, so i've been asked to investigate if a dhcp server on the first network could be used. network one has a mask of 255.255.248.0 and network two has a mask of 255.255.255.0.

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    0 Votes
    markp24

    Hi, I do believe you need a DHCP relay server in order for that to work. Ill see i can fin of a working example of this type of setup.

    +
    0 Votes

    Layer 3 is handling the routing so you can define whatever subnet mask is required for the networks via DHCP

    +
    0 Votes
    frank.williams

    If your switches cannot pass through DHCP/BOOTP packets then it is likely you would need a DHCP relay server in the 2nd subnet set up with 2 network adapters. 1 adapter configured for subnet 1 to allow the relay to chat back with the main DHCP server and another adapter configured for the 2nd subnet to allow DHCP messages to be 'relayed' to devices on that particular subnet.

    I think that is correct but it's been a little while since I configured anything like that ;-)

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    0 Votes

    And if your Switches are layer 3 as indicated they should be able to pass DHCP/BOOTP packets with a helper address of the DHCP Server on each Layer 3 interface/subnet that the DHCP Server does not sit on

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    0 Votes
    kjrees

    i think Markp24's example is when the subnet masks are all the same in each subnet. If you try and set up different scopes with different subnet masks then DHCP says:

    "the scope parameters are incorrect. Either the scope already exists or it's subnet address and mask is inconsistent with the subnet address and mask of an existing scope."

    basically in my example, there is a primary LAN with a mask of 255.255.248.0 and on a separate vlan the network has been configured with a mask of 255.255.255.0, but the vlan doesn't have a dhcp server. I think that in order for the Vlan's clients to use DHCP from the primary LAN, both the VLAN network and the primary LAN should have the same subnet mask or it won't work?

    in terms of connectivity, the primary LAN and the VLAN can communicate with eachother (ping) via static routes set up on the layer3 switch connected to the VLAN and also in RRAS on the ISA server machine direclty connected to the primary LAN.

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    0 Votes
    kjrees

    i'm thinking maybe a superscope might be the way to go(?)