Cable modem, ADSL router compatiblity

Posted on 2007-10-07
Last Modified: 2013-12-21

I'm using a cable modem provided by Virgin Media in the UK to access our 20mb broadband service and was wondering about compatibility with my router.
Basically when I connect my computer directly to the cable modem via ethernet, I get reasonable speeds.
However, when I connect the cable modem via ethernet to the ADSL router and then to my PC, our download speeds plumit.

Although the ADSL modem within the router is obviously not being used to connect to the internet, is there some compatibility issues with using a cable modem to provide internet to an ADSL router? and if yes, do I just need to replace the router with a compatible one (any recommendations?)

FYI, the cable modem is a Virgin Media E08C007 and the router, a Belkin Wireless G-Plus (F5D7231-4)

All ideas welcome,
Question by:digitalPencil
    LVL 2

    Expert Comment

    Looking quickly at the specs of the router, it has an ethernet WAN connection port (10/100). If this is correct, have you checked that the router is configured for 100 on the WAN port or is it auto sensing? It could be set to 10 and would therefore limit your speed to 10. I will look up some more detailed specs on it.
    LVL 50

    Expert Comment

    by:Don Johnston
    There are a couple things to consider:

    1) If the ethernet port on the modem is 100mbps and the WAN port on the router is 10mbps, then you just cut your speed in half.

    2) If the modem is capable of full duplex on the ethernet port and the router isn't, that could give you all sorts of problems (performance being one of them).

    3) It could me that the router just isn't designed to move traffic as fast as you want.

    Either way you look at it, the router is probably your bottleneck. You'll most likely need a router that has a 100mbps WAN  and LAN ports since you're operating over 10mbps.
    LVL 3

    Expert Comment

    Also check on Your ADSL router any QoS  and\or Load Balancing options, and disable it.
    BTW, what the difference between speed You have directly connected and over router? Upload and download affected?
    Possibly reason - Belkin may not be able to provide such speed for WAN2LAN, because it was created to serve ADSL connections, but currently I have no way to check it - no Belkin's in lab.
    LVL 2

    Expert Comment

    According to Belkin's Website it is a broadband router, there is no ADSL modem in it. Are the slow speeds you are getting over a wired connection to the router or through wireless? Unfortunately on Belkin's website there are no NTL/Virgin Media/Telewest settings specified for your router.
    LVL 6

    Accepted Solution

    Hello digitalPencil, it seems that you are not the only one to suffer this malady..
    1st make sure that you are not getting any magneto-electric interference, (make sure router/modem are away from any source capable of generating EMF)
    2nd:Try the following with TCP Optimizer:

    General Settings tab:
    Custom settings - check
    Modify All Network Adapters - check
    network adapter selection - your NIC
    MTU 1500
    TTL - 64
    TCP Receive Window - 64240
    MTU Discovery - Yes
    Black Hole Detect - No
    Selective Acks - Yes
    Max Duplicate ACKs - 2
    TCP 1323 Options:
    Windows Scaling - uncheck
    Timestamps - uncheck

    Advanced Settings tab:
    Max Connections per Server - 10
    Max Connections per 1.0 Server - 20
    LocalPriority - 1
    Host Priority - 1
    DNSPriority - 1
    NetbtPriority - 1
    Lan Browsing speedup - optimized
    QoS: NonBestEffortLimit - 0
    ToS: DisableUserTOSSetting - 0
    ToS: DefaultTOSValue - 80
    MaxNegativeCacheTtl - 0
    NetFailureCacheTime - 0
    NegativeSOACache Time - 0
    LAN Request Buffer Size - 32768
    Then select "Apply Changes" and reboot to take effect
    Hope this works for you...Booda

    LVL 10

    Expert Comment

    Can you provide the results of speed tests both on and off the router?

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