To assign DHCP form a single source or not?

Discussion in 'Wireless Internet' started by mikeraut, May 12, 2014.

  1. mikeraut

    mikeraut Guest

    I have a wireless network on a farm that extends for 16 kms. There are 5 various stops on the way where I have installed access points.
    The internet arrives on a Linksys E3000 that serves as a DHCP server as well.


    Along the way I have APs for the local users also configured as DHCP, but using a different range of IP addresses.

    What do the experts consider as best practice?

    Cisco AP ip 192.168.1.2 to 192.168.1.30
    Dlink AP ip 192.168.1.40 to 192.168.1.60
    TP-Link Ap ip 192.168.1.70 to 192.168.1.90

    This is the general configuration at the moment.
     
    mikeraut, May 12, 2014
    #1
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  2. Access points (i.e. no router enabled) do NOT have DHCP servers. Only
    routers have DHCP servers. Your three AP's seem to be configured as
    routers, not AP's. There's no problem with doing it that way except:
    1. You end up with double NAT, which can cause problems with remote
    control programs and server based programs.
    2. You cannot connect between computers on different sub-nets.
    3. Switching from one AP to another results in a change of client IP.
    4. You cannot easily access the 3 routers from the internet because
    they have two traverse TWO routers.
    5. With one big DHCP scope, there's no need to subnet.
    6. If you're into security and are using a RADIUS server for
    authentication, the double NAT can create problems.

    Unless you have complications that you didn't mention, methinks it
    would be better if you:
    1. Configure the three routers as access points.
    2. Disable the DHCP servers in the 3 access points.
    3. Move the backhaul cable from the "internet" port to the "LAN"
    port. More:
    <https://www.google.com/#q=router as access point>

    The one downside to using a single DHCP server is that if for some
    reason one of the connected access points is reset to defaults, the
    built in DHCP server will again become active. The symptom is that
    everything looks normal with IPCONFIG or ifconfig, but nothing gets to
    the internet. In order to more easily detect this problem, I've
    renumbered my networks to use something other than 192.168.0.xxx or
    192.168.1.xxx which are the defaults for most routers. For example,
    my office network is 192.168.111.xxx. If something gets reset, the
    connected client will show a 192.168.1.xxx address, which I know is
    wrong, and points to the obvious problem.
     
    Jeff Liebermann, May 12, 2014
    #2
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  3. mikeraut

    ps56k Guest

    for me -
    I like to have all my static IP stuff at the low end,
    then assign the DHCP ranges in nice numerical groups I can remember...
    ie - groups of 10, 20, 25, 50 - from each router or AP
    or on the 10's as you have BUT have them end on the 9's
    02 - 19 static
    20 - 29 09
    40 - 59 19
    60 - 69 09
    70 - 89 19
     
    ps56k, May 12, 2014
    #3
  4. mikeraut

    ps56k Guest

    I have a Linksys "160N" router/WAP with the router
    and the WAN/Internet port not being used.
    It is connected to an existing Linksys BEFSX41 router
    which normally has the DHCP function.
    I just turned on the DHCP server in the 160N WAP,
    and connected to it...
    SO, if the OP is using "routers", but only configs the WAP portion,
    then the DHCP scenario would work.
     
    ps56k, May 12, 2014
    #4
  5. So far, so good.
    Nope. You now have two DHCP servers. Assigning IP addresses is just
    part of the puzzle. You also have to deal with the default gateway.
    Both will set the default route to itself so that client computahs can
    connect to the interknot via the gateway router. However, your 2nd
    DHCP server is also pointing to itself, which is not the correct
    default route the internet. The symptoms are that everything looks
    like it works, with correct looking IP addresses, but any client that
    gets their DHCP assigned configuration from your "160N" thing, is not
    going to connect to the internet.

    You can probably make this work if your router firmware allows setting
    the DHCP assigned default route to an IP address other than itself.
    Most low end routers don't offer this feature. DD-WRT and other
    alternative firmware have that feature. You can also make it work
    with RIP2.

    Incidentally, make sure you don't duplicate IP addresses for the
    various routers.
     
    Jeff Liebermann, May 13, 2014
    #5
  6. mikeraut

    ps56k Guest

    sorry - I should have been more specific...
    for the test, I turned on the 2nd DHCP server in the Linksys 160N router,
    with the router portion not plugged in or used - maybe like the OP has -
    just using one of the LAN ports connecting to other local Linksys BEFSX41
    router.

    The 2nd DHCP settings were are manually config'd
    to point to the correct DNS, Gateway, etc
    and used a different IP range than my norm router assigns..

    It all worked fine - clients got all the correct settings,
    tested local & Internet - then turned it all off - back to just being WAP.
     
    ps56k, May 13, 2014
    #6
  7. That's the usual way. The DHCP service only works on the LAN side,
    not the WAN side.
    Ummm... I don't see where one plugs in the default route (gateway) in
    the WRT160N v3 setup:
    <http://ui.linksys.com/files/WRT160N/v3/3.0.00/>
    The ones that can be used as a secondary DHCP server have a "gateway"
    setting on the DHCP config page.
     
    Jeff Liebermann, May 13, 2014
    #7
  8. mikeraut

    ps56k Guest

    Jeff - you're right, I was too quick and didn't notice....

    Had my Android & iPad reboot and looked at local access,
    and then tried Internet from one of them...didn't look at the IP
    Status/settings.
    One just grabbed/renewed it's old lease & settings - so it worked -
    and the other grabbed the new IP, but nothing for GW & DNS - so it didn't
     
    ps56k, May 14, 2014
    #8
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