gigabit network with adsl modem

  • dazz

    i would like to build a gigabit network to connect the different computers at my home. I already have an 100Mb adsl router/modem but i have an hard time to find a 1000Mb one, so i came up with the idea of using a normal 1000Mb router or switch to put between the adsl modem and the computers. So i only use the adsl modem to connect to the internet and the gigabit router as dhcp to connect the different computers.

    But to get to the question. Will the 100Mb adsl router slow down my network? Will data travel like pc > gigabit router > computer or pc > gigabit router > adsl router > gigabit router > pc.

    My gut says it will go like in the first option but i have seen network hardware do some weird stuff.

    What do you think?

  • Answers
  • Sirex

    The "router" name applies if it is routing traffic between diffrent networks. In your case this means routing between your internal network, and the public internet. Your "adsl router" actually also contains a 100Mb switch, which just switches the traffic between the local network, and routes it out over the internet when needed. Its basically 2 network devices slapped together in one housing, 3 if you allow for the adsl modem it contains.

    You can just buy a gigabit switch and plug the adsl router into it. If you set the adsl router to do dhcp like normal the workstations will broadcast dhcp requests that'll reach the adsl router and they'll get told by the router to use the adsl routers ip as their 'default gateway' (as normal). such a setup will give you 1Gb traffic between workstations, 100Mb to the adsl router (not that youll likely trasfer files to it) and the internet connection speed will determine the link speed the other side of the router (obviously!)

    On my home network I have 4 old "adsl routers" which I use for the features they have (one as a print server, 2 as wifi access points, etc) without actually attaching the internet to them. I hang them all off a cisco gigabit switch. As long as your default gateway is set to the right device (the live router) you'll be dandy.

    edit: just remember if/when you buy the switch youll need at least number of workstations + 1, as the adsl router will be off it also.

  • Joe Taylor

    The ADSL Router will only determine speeds outside of your network. As long as its connected correctly.
    Your PC's will connect to each other through the GB Switch at 1Gbps

  • Ignacio Vazquez-Abrams

    The switch will run each port at its maximum capable speed. The speed of the interconnect between each port is independent of the speed of the ports, and is usually much faster (on the order of 10Gbps+).

    As for the actual packet situation, each machine will send packets destined for the local network out on the bare interface without a gateway, which will let the switch figure out the best way to route them (meaning that they won't go through the router).

  • Related Question

    windows home server - Abysmal transfer speeds on gigabit network
  • Vegard Larsen

    I am having trouble getting my Gigabit network to work properly between my desktop computer and my Windows Home Server. When copying files to my server (connected through my switch), I am seeing file transfer speeds of below 10MB/s, sometimes even below 1MB/s.

    The machine configurations are:


    • Intel Core 2 Quad Q6600
    • Windows 7 Ultimate x64
    • 2x WD Green 1TB drives in striped RAID
    • 4GB RAM
    • AB9 QuadGT motherboard
    • Realtek RTL8810SC network adapter

    Windows Home Server

    • AMD Athlon 64 X2
    • 4GB RAM
    • 6x WD Green 1,5TB drives in storage pool
    • Gigabyte GA-MA78GM-S2H motherboard
    • Realtek 8111C network adapter


    dLink Green DGS-1008D 8-port

    Both machines report being connected at 1Gbps. The switch lights up with green lights for those two ports, indicating 1Gbps.

    When connecting the machines through the switch, I am seeing insanely low speeds from WHS to the desktop measured with iperf: 10Kbits/sec (WHS is running iperf -c, desktop is iperf -s). Using iperf the other way (WHS is iperf -s, desktop iperf -c) speeds are also bad (~20Mbits/sec).

    Connecting the machines directly with a patch cable, I see much higher speeds when connecting from desktop to WHS (~300 Mbits/sec), but still around 10Kbits/sec when connecting from WHS to the desktop. File transfer speeds are also much quicker (both directions).

    Log from desktop for iperf connection from WHS (through switch):

    C:\temp>iperf -s
    Server listening on TCP port 5001
    TCP window size: 8.00 KByte (default)
    [248] local port 5001 connected with port 3227
    [ ID] Interval       Transfer     Bandwidth
    [248]  0.0-18.5 sec  24.0 KBytes  10.6 Kbits/sec

    Log from desktop for iperf connection to WHS (through switch):

    C:\temp>iperf -c
    Client connecting to, TCP port 5001
    TCP window size: 8.00 KByte (default)
    [148] local port 57012 connected with port 5001
    [ ID] Interval       Transfer     Bandwidth
    [148]  0.0-10.3 sec  28.5 MBytes  23.3 Mbits/sec

    What is going on here?

    Unfortunately I don't have any other gigabit-capable devices to try with.

  • Related Answers
  • Aaron Digulla

    I find it very odd that the speeds change so much when you change the server with iperf. I would expect the same performance in both directions. This looks like something hard to find. Try these options:

    1. Upgrade the BIOS and the network drivers. Download the latest version from the vendor site.
    2. Check the settings of your virus scanner. Disable it (and all other unimportant processes).
    3. Check for a virus.
    4. Make sure that duplex mode is active (no idea how to do that on Windows; on Linux, it's ethtool).
    5. Get a new cable; maybe a strand is bent/broken/flacky.
    6. Replace the oldest component with a newer one. Gigabit Ethernet should "just work" but there are combinations of devices which fail because of something odd.
    7. Get a new Gigabit network card. They are cheap and easy to install. Maybe one of the network ports if defective (so you can receive with high speed but can't send).
  • AndrejaKo

    If you can, try connecting the server and desktop directly with a different category 6 cable and running tests.

    To me it seems that the switch is making some problems on the way, but is not the main source of problems.

    Make sure that on both desktop and server same settings are selected for network connection. This should have been set up automagically, but it doesn't hurt to check for yourself.

    Take a look at duplex and speed on both interfaces. Also take a look at MTU size on both computers.

  • Helpful Advice

    Are the WD Green drives EARS model? WHS doesn't play well with these - they have a new advanced format. there is extensive discussion on WHS boards.