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Is my external IP my router or modem's address?

Discussion in 'Networking' started by daling, Nov 29, 2017.

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  1. daling

    daling Thread Starter

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    Assuming they are two separate units and not bridged.
    When you ping, tracert or DDoS attack or what-have-you my IP address, who/what do you reach ?
    Im understanding that a modem is just a media converter. It's got no IP address of its own.
    But then Wikipedia states (under "cable modem"): "With respect to the OSI model of network design, a cable modem is both Physical Layer (Layer 1) device and a Data Link Layer (Layer 2) forwarder. As an IP addressable network node, cable modems support functionality at other layers...] ...The Network Layer (Layer 3) is implemented as an IP host in that it has its own IP address used by the network operator to maintain the device."
    If it's not the modem's ip address, are they referring to TR-69..?
    A scan of an ISP subnet (e.g NMAP) returns/reaches routers or modems?
     
  2. TerryNet

    TerryNet Moderator

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    The modems that I have had have each been accessed from the LAN side via 192.168.100.1.

    Normally access via public IP from the ISP side goes directly to the router (or other device) connected to the modem. But ISPs can access the modem--maybe using public IP and a specific port, but maybe they have another way to address the modem.
     
  3. Couriant

    Couriant Trusted Advisor

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    To the consumer the modem is just a gateway. The external IP is your WAN port on the CPE, whether it's the router or computer.

    Terry, ISPs have a separate private IP address to access the modem. This IP is not visible outside of the ISP. (at least that's how it was for me)

    (why do i feel this is more of a homework question o_O)
     
  4. TerryNet

    TerryNet Moderator

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    Thanks, James.
     
  5. daling

    daling Thread Starter

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    Thanks, James.
    Not homework (wish I was that young). Been trying to understand and get a clear answer to this somewhat trivial question.
    BTW, lots of modems can be accessed (from internal network) via 192.168.100.1. Tried it myself yesterday.
    So nothing 'stops' at the modem and everything reaches the router?
    Do you know if a tracert gets a response from the modem as well?
     
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