Losing connectivity when I put in a switch or hub

Discussion in 'Network Routers' started by John McCabe, Jun 23, 2009.

  1. John McCabe

    John McCabe Guest


    I hope someone can give me some suggestions on a problem I'm having.

    Basically I have a PC and network printer connected to my D-Link
    DSL-G604T Wireless ADSL Modem/Router, which is in turn connected to
    the telephone line.

    I get a pretty poor signal from it around the house and thought it
    might be to do with it being in the study behind a solid wall so I
    intended to move it out to the hallway. Rather thatn running cables
    for the PC and printer out to it, I planned to connect those items to
    a switch or hub and run a single cable out to the router.

    Now, I've tried that, and it doesn't seem to work for some reason and
    I haven't a clue why not.

    I've tried 2 switches and 1 hub but the results are the same,
    basically very limited connectivity with what appears to be large
    packet losses.

    When I do it I can occasionally ping www.google.co.uk but more often
    than not at least 50% of the packets sent disappear. I can't even
    connect to the routers web browser configuration page at

    My PC has an Asus A8V Deluxe motherboard with on-board LAN. It's set
    up to use a static IP address of although I tried setting
    it up for DHCP at one point and, while it finally managed to lease an
    address, the connectivity to the outside world was still poor.

    I've also tried using the uplink port on the hub as well as using a
    normal port (on the hub and the switches) with a straight through and
    a crossover cable and nothing seems to make any difference.

    I imagine there's got to be something relatively obvious but important
    that I'm missing but I've no idea what; I'm used to sticking switches
    and hubs in to expand networks and they just work!

    Anyway - any suggestions anyone has would be very much welcomed.

    John McCabe, Jun 23, 2009
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  2. John McCabe

    Char Jackson Guest

    The PC and printer are connected to the Wireless router via wireless
    or via cable?
    Define "solid wall". What is it made of? Also, "poor signal" seems to
    relate to a wireless connection, but throughout your post you don't
    mention any wireless connections. Instead, you talk about running a
    cable from the PC and printer out to the router. Please clarify.
    So this is a purely cabled environment? Is anything connected via
    What are the IP addresses and netmasks of the LAN side of the router,
    the PC, and the printer? Are there any IP conflicts or mismatched
    If this is a wired connection and it's having trouble obtaining a DHCP
    lease, I would first be suspicious of the router.

    To make sure the PC is OK, you could connect the PC directly to the
    DSL modem to see if it reliably obtains an IP, Gateway, DNS, etc. Oh
    wait, you can't, because you have a combined modem/router.
    If the hub or switch is less than a few (5 or so?) years old, it
    almost certainly has autosensing ports, so either type of cable should
    work. I would stick with straight through patch cables and avoid
    crossover cables.
    Char Jackson, Jun 23, 2009
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  3. John McCabe

    John McCabe Guest

    Hi Char

    First of all thanks for replying.
    I think it's breeze-block with plasterboard over it.
    Sorry about that. I have another PC elsewhere in the house that's got
    a wireless card in it and never gets a very good connection, and I
    also use my phone on wi-fi but keep losing the connection. I've used
    my phone with other people's wireless systems without the same
    problems I have at home, so...
    I use the phone and the other PC wirelessly but, for the purposes of
    the problem I'm describing you can probably ignore the wireless
    aspect. All I'm trying to do is move the router out of the room it is
    currently in while minimising the number of cables that need to be
    trailed out.
    The PC is and the printer is The PC is assigned a static IP address
    and the printer gets it through DHCP. The router itself is
    I have no problems when the PC is connected directly in to the router,
    it's when it goes through a hub or switch first that things seem to go
    I've checked the specs of the modem/router and it certainly has
    autosensing ports (or so it says).
    John McCabe, Jun 24, 2009
  4. After inserting your switch plug a wired PC into it and ask for a new IP
    address using "ipconfig /release" followed by "ipconfig /renew" and see what
    your PC shows as it's "new" IP address, provided the PC has been set for
    DHCP. I find that until a wired device can work properly through a new
    switch I don't even bother messing with the added complexity of a wireless

    One thing that can cause problems, if the hub/switch is intelligent and has
    the capability of issuing an IP address all on it's own using DHCP then it
    may be set to assign an IP address in the same range as your existing
    connection. Two devices using on the same network usually won't
    work due to routing loops. If the manuals are not specific one easy way to
    check this is to unplug the hub/switch from the network. Then plug a wired
    PC (set for DHCP) into one of the user ports of the device. Then reboot the
    PC or use the "ipconfig /release" followed by "ipconfig /renew" (depending
    on the PC's software) and see what IP address the PC comes up with. If it
    starts with 169.xxx.xxx.xxx then the device is not providing DHCP and can
    most likely be considered a "dumb" hub. If on the other hand you get an IP
    address of 192.xxx.xxx.xxx then the device has DHCP capabilities and it is
    turned on creating possible conflicts.

    For what it's worth when using an actual router or "intelligent" device and
    having a PC come up with a 169.xxx.xxx.xxx address usually indicates a
    cabling problem between the router and PC or software issues with in the PC
    itself provided DHCP has not been disabled on the router.

    You don't want your router to be assigning IP values of 192.168.1.xxx AND
    your wireless hub doing the same unless they are actually a combined
    integrated unit. Then they usually come configured to issue DHCP values
    that will not conflict (wired/wireless).

    Hopefully some of this rambling will help you or others having similar
    GlowingBlueMist, Jun 24, 2009
  5. John McCabe

    Smiles Guest

    Do you set the wireless channel or is it set for auto
    How many other networks are in your area a "N band router will blow most
    G routers" bonkers

    I use BgInfo from
    to display IP on screen
    setup a batch file and place a shortcut on screen
    just click on shortcut to reissue network stats great for a laptop

    ****************************batch file
    ipconfig /release
    ipconfig /renew
    start "" "G:\program files\Bginfo.exe"

    call file what ever you want I use NewIP.bat

    next there are several programs around that plot signial strength over
    time see if you can find one and see what happens

    one of my Dlink boxes drops signal every two hour by its self traced
    problem to a metal bar about 24 inches away wich was reflecting signal
    back to unit and over powering transmitter control had to move unit 4
    feet to stop this

    try setting channel start at top channel and move down two channels at a
    time every week
    you might find a better channel for your location

    hope this helps
    Smiles, Jun 24, 2009
  6. John McCabe

    Char Jackson Guest

    That all looks good.
    Bad Ethernet cable? Do you have a spare cable you can swap with?

    Also, simplify things by connecting just two devices at first, whether
    it's the networked printer and the PC, or the PC and the router. Do
    things work as expected then? What do the status lights tell you
    (beside the Ethernet port on the PC and usually on the front of the
    switch/hub). Is the Link light solidly lit? Does the Activity light
    blink when data is being passed, and otherwise mostly off?

    Lastly, could this be a speed/duplex mismatch between the various
    Ethernet devices?
    To help rule out the concern of multiple DHCP servers on the network,
    as Glowing Blue Mist suggested, please provide the make and model of
    the switches and hub you've tried. I can't say I've ever seen a hub or
    switch with DHCP capabilities, but I tend to stay in the lower half of
    the various product lines and that's a bit of a premium feature when
    you're talking about hubs and switches.
    Char Jackson, Jun 24, 2009
  7. John McCabe

    terryc Guest

    Two things come to mind;
    1) you have steel in the line of sight of the wifi; stairs, bearers,
    chimney, racking, etc
    2) another device is corrupting the channel being used. Try changing it
    to others. Some guy reported his electric tooth brush was screwing up his
    wifi (used it to report brush pressure or something to a base unit).
    terryc, Jun 24, 2009
  8. The message <>
    A DHCP server is normally only found on routers. Switches (forget about
    hubs - they've been supplanted by switches for many years, even on SoHo
    kit) don't provide a DHCP serving function.

    However, the OP seems to have it arse about face regarding what's
    statically configured and what uses DHCP. Things like client PCs are
    best set up using DHCP assigned IP addresses and items like servers
    (print or file) are best set up with a static IP address _outside_of_
    the DHCP IP pool scope (but within the subnet range).

    The OP might try setting the router's DHCP scope to something like 1 to
    100 and assign the server and printer IP addresses in the range 101 to
    254 (assuming the router's own IP isn't on 254). I'm not certain how the
    DHCP server deals with static IPs within its scope (badly, I suspect) so
    a less fraught arrangement would be as suggested above. ;-)

    Johnny B Good, Jun 24, 2009
  9. John McCabe

    Char Jackson Guest

    I agree. That's why I asked about make/model info.
    While that's frequently the way it's done, it's not going to make the
    slightest bit of difference toward solving the OP's problem, so I
    didn't dwell there.
    Char Jackson, Jun 24, 2009
  10. John McCabe

    John McCabe Guest

    I really do appreciate your input, but we're getting a bit too caught
    up on the wireless side. The problem with low signal strength etc is a
    side issue that is the reason why I want to put the hub or switch in.
    The problem I'm confused about is why things are not working when I
    put the hub/switch in so ignore the wireless aspect for the moment.

    The switches and hubs I've used have been very simple unmanaged ones
    that I've borrowed from work and that I use at work with no problems.
    They don't have any intelligence in the form of DHCP servers or

    When I tried DHCP on my wired PC, at the second attempt it was
    assigned (my router is set up to assign DHCP addresses
    from upwards, and my printer already had .100 and .101

    John McCabe, Jun 25, 2009
  11. Ok John,
    You've most likely done this already but here is a suggestion on how I would
    work on the problem.

    Go into your PC's LAN settings and lock the LAN port at 10 mbps rather than
    Auto or the other two settings of 100 or 1000. This is to eliminate the
    port of the router and PC from searching for a matching speed and will force
    them to meet at 10 mbps.

    Then take your PC and hook it up directly to the router.
    Ping and verify you have a clean stable connection.
    If it is not stable you may need to reset the router in order for it to
    match the speed of your PC.
    Once you have this connection stable test it with your other cables.

    Then with two tested cables hook one of the "dumb" switches uplink port and
    the other tested cable from the hub to the PC. If the Uplink port does not
    get a link LED you may need to push a small button that may be near the
    uplink port. This is to manually set the device for a straight or cross
    over cable. With no button and no link LED you may need to use a cross over
    cable between the router and the uplink port. Once again reset the router
    to insure it's matching the speed of the switch and then do the ping tests
    again. If they are good you might be able to raise the speed of your LAN
    port to 100 provided the switch can handle the increase in speed.

    Too many times on older routers and such I've seen the ports bouncing from
    one speed or another with neither device becoming the "master" and choosing
    a port speed to stay at. Newer switches and routers usually do not have
    this problem any more as the internal sampling rates of the ports are much

    Good luck.
    GlowingBlueMist, Jun 25, 2009
  12. John McCabe

    John McCabe Guest

    I've tried 3 cables; two straight and one crossover, and I also tried
    one of the straight ones direct from my PC to the router to check it
    worked that way. I don't think there are any problems with the other
    cables as they're borrowed from work and in my drawer as spares. I
    also buzzed them through to check the connections although obviously
    that doesn't prove the plugs are connecting in the sockets properly.
    I've done that. The last time I tried it I didn't bother powering on
    The activity light is mostly on and blinks when there is traffic on
    the switch (3COM OfficeConnect Dual Speed Hub & Switch, or D-Link
    DES-1005D). For what it's worth, they don't show a lot of activity.

    One other thing I should mention, and I don't mean this in any way to
    be offensive, is that you don't need to treat me as a newbie; I'm a
    software engineer working on satcoms applications and I use these
    switches and things at work all the time! I've already asked around
    here including our network support guys and they've not come up with
    Mmm - yes - that is a possibility. The PC network interface is an
    on-bard Marvell Yukon gigabit thing and we're aware of issues here
    where some devices can autonegotiate half-duplex connections. I
    haven't got round to setting the device to fixed 100MBPS Full-Duplex
    to try it yet.
    Yes, I agree. I've mentioned the devices above and as far as I'm aware
    none of them have DHCP capabilities.

    John McCabe, Jun 25, 2009
  13. John McCabe

    John McCabe Guest

    FWIW - there's no reason why on a small network like mine, I shouldn't
    use static ip addresses for my PC, especially as it was easier to
    configure the router to do that _and_ set it up for port-forwarding to
    a specific IP address through the firewall. Also the printer defaulted
    to DHCP and I didn't see the point in changing that.

    Now, if I had a lot of PCs, perhaps I would have done it differently.
    John McCabe, Jun 25, 2009
  14. John McCabe

    John McCabe Guest

    As I mentioned to someone else, I appreciate your input, but I'm not
    really interested in the Wi-Fi issue at this time; it's the problem
    with the wired connection through a hub/switch to the router that's of
    more concern.
    John McCabe, Jun 25, 2009
  15. John McCabe

    John McCabe Guest


    Thanks for that suggestion, that's the next thing I had planned. I'd
    actually gone in to the settings for the Autosense/10MBPS/100MBPS etc
    at one point but ran out of time so hadn't tried changing it.
    John McCabe, Jun 25, 2009
  16. John McCabe

    Smiles Guest

    ok take your computer, wire it directly to the second hut/switch with
    nothing else connected to this network

    use your browser and log into this device should be which
    would be in conflict with primary network
    then set its wan to a network address in your primary network say then set its lan/DHCP to start at and ending

    then reconnect all to your network rebooting each

    when this unit reconnects to your network it will have an address on the
    network and issue IPs on the network as apposed to failing when it gets
    locked out by an IP conflict

    this is how my network is done
    Smiles, Jun 25, 2009
  17. John McCabe

    Char Jackson Guest

    His switches are unmanaged - no login capability, no DHCP, no IP
    Char Jackson, Jun 25, 2009
  18. John McCabe

    Char Jackson Guest

    No disagreement there. You already showed that there are no IP/mask
    conflicts, so it doesn't matter in the slightest how the addresses got
    assigned. On my own network, everything is set up for static IP. For
    some people, maybe even most, DHCP might be easier, but either way
    Char Jackson, Jun 25, 2009
  19. John McCabe

    Char Jackson Guest

    I'm pinning some hope on that, so let us know! If the problem isn't
    there, maybe it's some kind of weird incompatibility that can only be
    fixed with a firmware update, but that seems unlikely.
    No offense taken. Thanks for that.
    Char Jackson, Jun 25, 2009
  20. John McCabe

    terryc Guest

    1) cables.
    2) auto neg to auto neg usually equals disaster.
    2) switch management?
    30 switches can take a few seconds to learn about changed gear.
    4) tried pinging the opposite end from each end?

    Might be better to start a new thread for this. Did a little search, but
    couldn't find your hardware details, brand/model, of all the gear.
    terryc, Jun 26, 2009
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