DHCP,DNS Servers

Posted on 2004-11-11
Last Modified: 2012-05-05
Hi all,

  I have some knowledge on DHCP ,DNS servers and what they do. But I fail to understand where actually these servers reside so that DHCP server allot a Ip address to the terminal and DNS server will resolve Name to Ip address.

Do they reside somewhere in the internet or do they sill sit in the network.

Please explain to me this cleary.

Thanks in advance,
Question by:dineshb_2001
    LVL 41

    Assisted Solution

    your dhcp server will reside on your network (or your isp's network)
    as for the dns server, this gets more complicated, it depends
    some may reside on your network, and some on the internet
    LVL 5

    Accepted Solution

    DHCP server has to sit inside the LAN, since the DHCP request is a broadcast and it doesn't pass the router.

    DNS can be anywhere - inside/outside the LAN.

    DHCP server gives the IP to a workstation together with other parameters of the network: Subnet mask, default gateway, DNS Server, etc.

    So the flow for the station which is configured as DHCP Client and is booting up, goes like this:

    NIC is initialised, a broadcast DHCP server is sent throughout the LAN with a request for an IP address from an available DHCP server.
    In case DHCP server is online and has free IP addresses to give, it answers the machine and gives it an IP address together with DNS server address.

    In case DNS is in the LAN (same subnet) - machine can access it on the same subnet, in case the IP of the DNS server is external (Behind a router: not local but for example on ISP site) the machine can access it through the default gateway.
    LVL 8

    Assisted Solution

    that answer to that question is both... ISP's will have DHCP servers issue WAN addresses to its clients and DNS servers to service their neeeds...  For DHCP... if you will using a router/firewall that NAT's the connection to your ISP and don't want to manually setup IP addresses on all the workstation on your network you would need to setup a DHCP server in your network... this could be done on a router/firewall that supports DHCP (most do) or on a windows server product...

    For DNS servers you have two options... you can configure DNS to give all the client PC's the address of the ISP's DNS servers or you can setup your own DNS server (on a windows or unix box) internally and forward all request from your DNS server to the ISP's... these options have advantages and disadvantages... first... if you are going to run a domain network you have to have an internal DNS server and if the clients don't use the internal DNS server then they could experience long logon times as they attempt to locate a domain controller.... also... if you don't run your own internal DNS server you will need to have some sort of broadcast resolution working (Netbios) so you don't have to setup HOSTS files on each workstation to allow computer to resolve internal computer names since the ISP DNS server would not have records to resolve those names...

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