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internet connection

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  • internet connection

    I configured my router to receive connection from the internet via a modem. I read where the isp will provide you with an ip address dynamically if you use the ip address dhcp command on the interface of the router that connects to the modem.

    I also have a dhcp pool on my router that assigns private ip addresses to devices on the network.

    Why does the interface connected to the modem opt to use an ip address provided by the isp's dhcp pool and not the pool that i created. How does it know the difference?

    Is it because the modem is connected to this interface? Please explain.
    Last edited by thickSkin; 6th September 2009, 05:45.

  • #2
    Re: internet connection

    That's all normal. Which Cisco router do you have?
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    • #3
      Re: internet connection via cisco router

      its a 831 cisco router


      • #4
        Re: internet connection

        This is normal. Your router gets the the address from the ISP because it send the DHCP address request on the external interface, whereas your DHCP pool will be on the internal interface. Your external IP will be one in the ISP's range (allocated to you, if you have a static address from them).

        I have an 877. I have a single static from the ISP and I use NAT internally.



        • #5
          Re: internet connection

          ISPs generally do not use DHCP for their customer connections.

          The dynamic IP allocation that you mention is done by IP Negotiation and not DHCP. IPCP packets are sent to the destination which then negotiate the relevant options as required.
          Infrastructure Architect
          CCNA, CCNA Security, MCSE, JNCIS