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piotr_dobrogost's avatar
piotr_dobrogost
Aspirant
Mar 06, 2021
Solved

Nighthawk R8000 DHCP on WAN port not working

I replaced Netgear WNR3500L with Netgear R8000. I had WNR3500L's WAN port connected to TP-LINK TD-W8960N DSL modem (setup in router mode) and obtaining IP address and DNS servers from it using DHCP. ...
  • antinode's avatar
    antinode
    Mar 06, 2021

    > [...] I have "Internet IP Address" set to "Get Dynamically from ISP"
    > in "Internet Setup". [...]

     

       What about all the other Internet Setup settings?  Did you try
    letting the set-up wizard do what it does?

     

    > [...] Why?

     

       Who knows?  With my weak psychic powers, I can't see any of the LED
    indicators on any of your devices, or any of the R8000 Internet Setup
    settings (save one), or the configuration of your old WNR3500L.  Could
    be a bad Ethernet cable, for all I know.

     

       If you connect a computer to the TD-W8960N, does _it_ get good IP
    parameters?  (Namely?)

     

    > [...] TD-W8960N DSL modem (setup in router mode) [...] "I connected
    > R8000 the same way [...]


       Why, exactly, are you arranging a cascade of routers, instead of
    using one router (modem and router, or modem+router and wireless access
    point)?  Cascading multiple routers can cause multiple problems (double
    NAT, for example), even when you get such an arrangement to work.

antinode's avatar
antinode
Guru
Mar 06, 2021

> [...] I have "Internet IP Address" set to "Get Dynamically from ISP"
> in "Internet Setup". [...]

 

   What about all the other Internet Setup settings?  Did you try
letting the set-up wizard do what it does?

 

> [...] Why?

 

   Who knows?  With my weak psychic powers, I can't see any of the LED
indicators on any of your devices, or any of the R8000 Internet Setup
settings (save one), or the configuration of your old WNR3500L.  Could
be a bad Ethernet cable, for all I know.

 

   If you connect a computer to the TD-W8960N, does _it_ get good IP
parameters?  (Namely?)

 

> [...] TD-W8960N DSL modem (setup in router mode) [...] "I connected
> R8000 the same way [...]


   Why, exactly, are you arranging a cascade of routers, instead of
using one router (modem and router, or modem+router and wireless access
point)?  Cascading multiple routers can cause multiple problems (double
NAT, for example), even when you get such an arrangement to work.

  • piotr_dobrogost's avatar
    piotr_dobrogost
    Aspirant
    Mar 20, 2021
     

    > What about all the other Internet Setup settings?

     

    I am pretty sure "Internet IP Address" is the only relevant option as long as we are discussing getting IP address.

     

    > Did you try letting the set-up wizard do what it does?

     

    No as I'm used to setting these things myself and do not want any wizard to set things behind my back.

     

    > If you connect a computer to the TD-W8960N, does _it_ get good IP
    parameters?  (Namely?)

     

    Good advice and I should have checked this before posting. The computer did not get ip when connected to the TD-W8960N which pointed to some problem with the TD-W8960N and not R8000.

    Originally I had the following DHCP settings on TD-W8960N:

    Start IP Address: 192.168.1.2

    End IP Address: 192.168.1.3

    and a static IP lease 192.168.1.2 set for WNR3500L.

    When I replaced WNR3500L with R8000 I changed static lease for WNR3500L (in case I connect it back someday) to 192.168.1.3 and set a static lease for R8000 to 192.168.1.2 (the previous IP address reserved for WNR3500L). Funny enough with these settings DHCP just stopped working. Extending ip range by changing "End IP Address" from 192.168.1.3 to 192.168.1.4 made DCHP work again. Really wired. It seems like implementation of DHCP in TD-W8960N is such that when the number of static leases is the same as the number of IP addressed configured by means of start/end IP range the DHCP is inactive. In other words it seems like the list of static leases counts toward the limit of the number of IP addresses configured by means of start/end IP range.

     

    Now I am curious how this looks like in other routers and if the behaviour of TD-W8960N is the norm or the exception?

     

    > Why, exactly, are you arranging a cascade of routers, instead of
    using one router (modem and router, or modem+router and wireless access
    point)?  Cascading multiple routers can cause multiple problems (double
    NAT, for example), even when you get such an arrangement to work.

    The only reason for this setup is that I did not like not being able to reach modem (web UI) from LAN when I had modem bridged with the rourter.

     

    Thank You antinode for helping me with this and I am sorry for getting back so late.

     

     

    • piotr_dobrogost's avatar
      piotr_dobrogost
      Aspirant
      Mar 22, 2021
      piotr_dobrogost wrote:
       


      > Why, exactly, are you arranging a cascade of routers, instead of
      using one router (modem and router, or modem+router and wireless access
      point)?  Cascading multiple routers can cause multiple problems (double
      NAT, for example), even when you get such an arrangement to work.

      The only reason for this setup is that I did not like not being able to reach modem (web UI) from LAN when I had modem bridged with the rourter.

      Hmm, according to https://superuser.com/a/993785/664 answer to the question "How do I access my modem's GUI when it's in bridged mode?" it is possible to access  modem when it is in bridged mode...

      • antinode's avatar
        antinode
        Guru
        Mar 22, 2021

        > The only reason for this setup is that I did not like not being able
        > to reach modem (web UI) from LAN when I had modem bridged with the
        > rourter.

         

           I'm now at least as confused as I was before.

         

        > [...] I changed static lease for WNR3500L [...]

         

           Terminology: A "static" address is configured on the device itself.
        What you configure on a (DHCP server on a) router is a reserved dynamic
        address, not a static address.  Either one should fix the address of a
        device, but some implications are different.

         

           A static address is static, not leased.  A dynamic address is leased.
        A "static lease" is not a thing.

         

        > Originally I had the following DHCP settings on TD-W8960N:
        > Start IP Address: 192.168.1.2
        > End IP Address: 192.168.1.3


           Why such a small DHCP pool?  None of this makes sense to me.  A
        router has two network interfaces, LAN and WAN/Internet.  Either or both
        of them can use DHCP, so saying only "DHCP" does not describe what
        you're doing.

         

           You have a TD-W8960N DSL modem+router.  Do you want to use it as a
        modem+router, or as a modem only, or what?

         

           You have an R8000 which you want to connect to the TD-W8960N?

         

           If you want the TD-W8960N to be a modem+router, then I suggest that
        you configure the R8000 as a wireless access point.  That would leave
        the DHCP server in the TD-W8960N as your only DHCP server, so its pool
        should be normal (".2" - ".254", for example).

         

           If you want the TD-W8960N to be a modem only, with the R8000 as a
        full-function router, then you need more information on the TD-W8960N,
        and a Netgear forum might not be the best place to get it.


           Among the things which I don't know about a TD-W8960N is whether you
        can talk to its management web site when it's in a modem-only mode.

         

        > Hmm, according to [...]

         

           I doubt that any of that applies to you.  If you had a DOCSIS
        cable-TV modem, then you should be able to find it at "192.168.100.1",
        but that's not what you have.  It's not obvious to me that much of the
        rest of that discussion makes sense, or applies to your situation.  (But
        part of that might be because I don't understand what you want to do.)

         

        > [...] it is possible to access modem when it is in bridged mode...

         

           It depends on the modem.  But, generally, once a modem has been
        configured, there's little reason to deal with it.