RT31P2 - How to get a static IP address on LAN

Discussion in 'Wireless Internet' started by cjtwantstoknow, Aug 25, 2005.

  1. I have the following configuration:

    Cable Linksys DLink Wireless
    Modem ------ RT31P2 -------- DI-604 -------- Router ------- PCs
    NAT & DHCP Router | no NAT
    | no DHCP
    |
    |---- Desktop PC

    I'd like to configure the Desktop PC as an FTP server and I have setup
    port-forwarding on the RT31P2 and the DI-604 routers. It works except
    that the DI-604 sometimes gets another IP address from the RT31P2 and
    causes the port-forwarding to no longer work because the IP address
    of the downstream router has changed.

    The RT31P2 sits in front of the DI-604 because the RT31P2 is for voip
    service and it gives voice traffic priority over other traffic (QoS).

    The DI-604 has a static DHCP function that allows me to tie the Desktop
    PC
    to a specific address on the DI-604. The static DHCP keeps the Desktop
    IP
    address constant.

    Is there a way to keep accomplish this?

    It would be great if the RT31P2 had static DHCP - perhaps there's
    another way
    to accomplish the same function.

    Can I configure the DI-604 to have a static address and turn off
    DHCP/NAT on the
    RT31P2? A static WAN address on the DI-604 requires I define also DNS
    server addresses
    and I'd like to keep getting those automatically.

    Any other suggestions?

    Chris
    cjtwantstoknow
     
    cjtwantstoknow, Aug 25, 2005
    #1
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  2. cjtwantstoknow

    David Taylor Guest

    It would be great if the RT31P2 had static DHCP - perhaps there's
    There's no such thing as static DHCP, you can create a reservation but
    then there's no point using DHCP in that case for one machine.

    Why not just leave the Dlink out completely, it serves no purpose and
    just configure a DHCP scope for the required number of PC's and then
    give the desktop a static IP address that does not exist in the DHCP
    scope?

    David.
     
    David Taylor, Aug 25, 2005
    #2
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  3. yeah replace the 604 with a switch
     
    Jorge Padrone, Aug 25, 2005
    #3
  4. This is the first time I've ever seen anyone try to use *THREE*
    routers in series. Is there some reason you think you need the extra
    two routers? The RT31P2 is an ethernet router with all the features
    that the other two routers duplicate (except wireless).

    Start by removing the DI-604. It does nothing useful.

    Then, reconfigure the Wireless Router (no model number specified) into
    an access point. Do not connect anything to the WAN port. Setup the
    IP address to be in the same /24 group as the RT31P2 but on a
    non-duplicated IP address. Disable the DHCP server. Now, it's just
    an access point.

    Plug the PC's and Desktop PC into the RT31P2 LAN ports.
    Well, if you insist on using the DI-604, dive into the RT31P2 and see
    if it has a feature called "static DHCP". If so, configure it to give
    the MAC address of the DI-604 router always the same IP address. I
    couldn't find anything in the manual at:
    ftp://ftp.linksys.com/pdf/rt31p2_ug.pdf
    that would indicate that it has this feature. The only alternative is
    to assign a static IP address on your desktop PC that's acting as an
    FTP server, and port forward the RT31P2 to point to this static IP
    address. Please pick an IP address that is NOT inside the DHCP
    assigned IP address range of the RT31P2.
    Yes, the RT31P2 *MAY* be installed in front of an existing router.
    However, there's no reason why it must be installed in front of this
    router. The recommended setup in the manual does not show the extra
    router. The RT31P2 duplicates all the functions of the DI-604 with
    the added complexity of dealing with two routers. There's no need to
    do that. Just use the RT31P2 and sell the DI-604.
     
    Jeff Liebermann, Aug 25, 2005
    #4
  5. Jeff,

    Thanks for your advice!

    I use the DI-604 because it gives me the ability to assign an IP
    address to a MAC address in the static dhcp setup. Since I share the
    wireless network with others, it allows me to assign specific IP
    addresses that in turn can be specified in the firewalls on my PCs.
    This keeps my neighbors out of my PCs and me out of theirs.
    I like to keep the desktop and the wireless clients on the same
    network/router because then I don't have to deal with port-forwarding
    to support Microsoft file sharing.

    The RT31P2 doesn't support static dhcp so that's why I don't use it
    instead of the DI-604. As far as the wireless device goes, it's there
    because it is physically situated away from everything else and using
    its LAN ports is not possible. The desktop needs to be wired because
    certain applications require a network card and don't work with
    wireless cards.

    I'll probably end up plugging the desktop (the FTP server) into the
    RT31P2 and assign it a fixed IP address.

    BTW - The wireless device is a Parkervision WR1500.

    Chris

    cjtwantstoknow
     
    cjtwantstoknow, Aug 25, 2005
    #5
  6. cjtwantstoknow

    David Taylor Guest

    I use the DI-604 because it gives me the ability to assign an IP
    Like several have said, there's no need to use DHCP and then defeat it
    by reserving an address to a machine like you are doing. Just assign a
    static IP address to the box but use one outside of the DHCP range.
    That would still be the case.
    So configure a static IP address, job done.
    Jeff said use a switch, that'll work just fine.
    Best solution.
     
    David Taylor, Aug 25, 2005
    #6
  7. Well, I guess that's one way of doing it.
    Well, that will work, but if you want to preserve your existing setup
    and make it easy to get to your desktop PC from other machines, all
    you need to do is assign a static IP address to the DI-604 *WAN* port.
    I think the RT31P2 is 192.168.15.1. Use something like:
    IP 192.168.15.15
    GW 192.168.15.1
    NM 255.255.255.0
    DNS 192.168.15.1
    Then, port forward 20 and 21 (ftp) on the RT31P2 to 192.168.15.15 and
    again in the DLink DI-604 to the IP address of the ftp server.
    Thanks.
     
    Jeff Liebermann, Aug 25, 2005
    #7
  8. cjtwantstoknow

    Miguel Cruz Guest

    You can absolutely use DHCP to manage static addresses.
    Yeah, that was my question too.

    miguel
     
    Miguel Cruz, Aug 25, 2005
    #8
  9. cjtwantstoknow

    Miguel Cruz Guest

    Only if they're cooperative. It's easy enough for them to clone a MAC once a
    "trusted" machine is turned off.

    miguel
     
    Miguel Cruz, Aug 25, 2005
    #9
  10. cjtwantstoknow

    David Taylor Guest

    You can absolutely use DHCP to manage static addresses.

    I am fully aware of reservations! My point here is that the definition
    of DHCP is Dynamic and there's no such thing as Static Dynamic any more
    than there's hot/cold or up/down at the same time it is not possible to
    have opposites like this, a DHCP reservation is a DHCP reservation but
    you cannot manage a clients static address, only hand out the same
    dynamically assigned reserved address by a DHCPOffer upon the
    DHCPRequest or DHCPRenew packets. Yes, i'm being picky! :)

    This is unfortunate blatant abuse of terminology, I'll blame Linksys and
    Dlink for this at this time.

    It's rather pointless setting up DHCP to manage one machine as a static
    address, that's more work than is required.

    David.
     
    David Taylor, Aug 25, 2005
    #10
  11. cjtwantstoknow

    David Taylor Guest

    Only if they're cooperative. It's easy enough for them to clone a MAC once a
    or change their IP addresses
     
    David Taylor, Aug 25, 2005
    #11
  12. Thanks Jeff!

    I didn't realize that I can specify the router as the DNS server. I
    guess the RT31P2 just forwards the request.

    I assigned a static address to the DI-604 (outside dhcp range) and it
    works as desired.

    I realize that I have more devices than needed. Perhaps I'll eliminate
    the DI-604 and assign my machines to fixed IP addresses instead.

    Chris
     
    cjtwantstoknow, Aug 26, 2005
    #12
  13. cjtwantstoknow

    David Taylor Guest

    I didn't realize that I can specify the router as the DNS server. I
    Sell the DI-604 on ebay ;)
     
    David Taylor, Aug 26, 2005
    #13
  14. Can you get enough to make it worthwhile? They're pretty cheap.
     
    Derek Broughton, Aug 26, 2005
    #14
  15. cjtwantstoknow

    David Taylor Guest

    Can you get enough to make it worthwhile? They're pretty cheap.

    They are cheap but it's redundant right now so might as well make a few
    pennies. :)
     
    David Taylor, Aug 26, 2005
    #15
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