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Forward ISP dhcp to a lan client

Discussion in 'Asuswrt-Merlin' started by andresmorago, Mar 18, 2019.

  1. andresmorago

    andresmorago Regular Contributor

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    Hello

    I have a ac68u router. It’s connected on the Wan port to a cable modem on bridge mode so router gets a public IP address from isp. Cable modem does nothing but acting as a bridge. On this mode, it will assign public ips to whatever I connect to its switch.

    Is it possible that, while preserving this setup, I could configure the asus router to pass though the isp dhcp to a client connected on the lan side of if? I need a lan device to acquire a public ip.


    Thanks
     
  2. L&LD

    L&LD Part of the Furniture

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    Does your ISP give you more than one public IP address?
     
  3. andresmorago

    andresmorago Regular Contributor

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    Yes. I can connect up to 3 devices on the cable modem Switch and all of them will get a different public ip. Total purchased bandwidth will be divided into all devices
     
  4. eibgrad

    eibgrad Regular Contributor

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    Rather than actually assigning public IPs to devices on the LAN, the following would probably be a better approach.

    https://wiki.dd-wrt.com/wiki/index.php/One-to-one_NAT

    Although the above wiki is for dd-wrt, it actually applies to any third party firmware. The idea is to bind all your public IPs to the WAN of your primary router, but then port forward those public IPs to LAN ips. By doing so, the LAN devices retain their local IPs (so they can still communicate w/ other devices on the LAN), but *appear* to have their own *public* IPs thanks to the port forwarding.
     
  5. andresmorago

    andresmorago Regular Contributor

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    Thanks for the info. But I believe that approach is when you have static public ip addresses. In my case, I rely on my ISP’s dhcp service to obtain public ip’s
     
  6. eibgrad

    eibgrad Regular Contributor

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    Not clear to me the purpose or value of having multiple dynamically assigned public IPs, esp. if all but the public IP assigned to the WAN of the primary router are to be assigned *through* that same WAN. Why not just place a switch behind the modem and connect the WAN of the primary router, and the LAN port of the other devices to be assigned public IPs to that switch? Or else place those other devices on their own VLANs (or WLAN) w/ no local DHCP server (amounts to the same thing)?
     
    andresmorago likes this.
  7. andresmorago

    andresmorago Regular Contributor

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    hello
    i really appreciate your help. without getting into details of looking the purpose or value of having multiple public addresses, is there a way to achieve this?

    thanks
     
  8. L&LD

    L&LD Part of the Furniture

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    Did you try what was already suggested by eibgrad? Does that not give you what you need?
     
  9. andresmorago

    andresmorago Regular Contributor

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    thanks. i looked into that option but it doesnt apply to me since i dont have static public ip addresses
     
  10. ColinTaylor

    ColinTaylor Part of the Furniture

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    I can't see the logic in what you're trying to do. Your clients can query DHCP by themselves so you don't need to connect them to your router for them to get their public IP addresses. Just connect them to your modem via a switch as @eibgrad suggested. I can't think why this won't work and it would be much simpler than using some convoluted pass through on the router.:confused:
     
    L&LD likes this.
  11. andresmorago

    andresmorago Regular Contributor

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    Ok.
    Thank you all for your advices. I will do it that way
     
    L&LD likes this.
  12. L&LD

    L&LD Part of the Furniture

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    I was suggesting the method in post 6 too. :)