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Cable modem, ADSL router compatiblity

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,
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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.
Don JohnstonInstructor
Top Expert 2015

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.

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.

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