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DHCP DNS Server Override (& PXE Windows Boot Setup)

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  • DHCP DNS Server Override (& PXE Windows Boot Setup)

    Hello All!

    Right, I have a cisco 2600 with two ethernet if's, one internal (with lots of complicated vlans, static ips etc) and the other to the internet (we use overloaded NAT).

    Very simply: the external if (FastEthernet 0/1) gets its IP, DNS servers, Gateway etc from the DHCP server at Virgin Media Business. The IP we are provided with is essentially static as it is bound to the routers external MAC address.

    Q1: - How can I override the DNS server that is obtained from Virgin Media's DHCP server, i.e. I dont want to use Virgin Media's, I want to use those supplied by our web filtering company. Currently my workaround is: When internal clients request a DHCP lease from the router I give them the IP's of the web filtering companies DNS servers. I would rather not have to do this, just give them the IP of the router and use DNS forwarding.

    So far, but doesn't override the servers:
    ip name-server <Web filtering DNS 1>
    ip name-server <Web filtering DNS 2>
    interface FastEthernet0/1
    ip address dhcp
    ip nat outside
    ip nat enable
    ip virtual-reassembly
    duplex auto
    speed auto
    ip dns server

    Any help would be apreciated, it doesnt really matter too much, the current system works, just more of a curiosity?

    Q2: We did have the DHCP server on a Windows Domain Controller with RIS/PXEBoot setup. Is there any easy way to set the DHCP scopes on the Router to announce that there is a RIS server on a nearby windows server 2003 box now that the DHCP server has been moved to the Cisco?

    Thanks again,


  • #2
    Re: DHCP DNS Server Override (&amp; PXE Windows Boot Setup)

    I dont see a local dhcp pool for your internal clients in your config but you can modify the dhcp pool on the router and set the dns servers to what you want.

    dns-server (in dhcp configuration mode)

    The ip name-server x.x.x.x is just for dns resolution for the router itself by default. You can have the router function as a fowarding proxy dns server.

    ip dns-server

    ip name-server x.x.x.x
    ip name-server x.x.x.x

    Then just set your dns server for your clients in the dhcp pool on the router to the router itself. It will then forward requests to the server in the ip name-server command and cache the results.
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