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Internet Cable modem only speeds good, they slow when a router is in place

A residential client I have has found (in Lower Alabama) when using only the Mediacom modem to the his PC with an dynamic WAN IP the speeds are as they should be. When he places a router/firewall on the LAN side everything slows way down. He should have 11 MB down 1.5 MB up. With the router in place he is getting about 2.15 MB down and .009 - .51 MB up.

We have tried two different routers, both lower end. The first thing I did was have him purchase a Ethernet only router and branch the wireless router from there. No difference. I use COX and I had some issues but when I replaced the DOCSIS 1.0 modem issued by COX with a DOCSIS 2.0 - everything worked fine. But my troubles were only getting 10 -11 MB down instead of 28 MB down. Upstream was OK. Now I run as advertised by COX..
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Many consumer-grade routers have a 10Mb jack and controller on the WAN/Internet port, because the average cable connection provides only about 6Mb download speeds.

Have you tried speed testing through the router from LAN to WAN when it's not connected to the modem?
That should help eliminate cables and other components that aren't in the picture when connected directly to the modem.

Then you could also try a different routers... e.g. the D-Link DIR-655 (on amazon) has gigabit ports on the LAN and WAN sides.


The DLink router they have is D-Link EBR-2310 Ethernet Broadband Router: Interfaces:  WAN : 1 x 10Base-T/100Base-TX - RJ-45 ¦ LAN : 4 x 10Base-T/100Base-TX - RJ-45 .

Perhaps I am missing something but last time I checked a modem was needed to connect to the internet. Do you have a way to check through-put without actually being authenticated to your IPS?

If indeed it is only a 10MB port it still should give him better upand down stream speeds. If I'm missing something here please point out what it is.

Thank you.
> Perhaps I am missing something but last time I checked a modem was needed to connect to the internet.
An internet connection is required to check throughput of the modem, but you've already established that the chokepoint isn't in the modem, since the ISP's advertised speed is achieved when connected directly to the modem.

All that's required to check the throughput of the router is 2 computers with network adapters (technically, 1 computer with 2 network adapters could test throughput of the router, but that's actually more complicated), a few gigs of free hard drive space on each one and some files of varying sizes. A few CD or DVD ISO files is probably enough for a quick picture of transfer speeds between the client's computer and, say, a laptop you take with you to the premises.

> Do you have a way to check through-put without actually being authenticated to your IPS?
I typically use NetMeter, which is free, though there are many utils available that will do the same job. Some free; some not... some require an internet connection to track stats long term; most do not.
Anyway, NetMeter and its source can be downloaded from http://www.metal-machine.de/readerror/index.php

I recommend the beta version. The last 'non beta' didn't follow the 'always on top' setting in its options correctly, for one thing.

The computer connected to the WAN port should have a static IP, and the WAN port on the router can be set to a static IP in that same subnet (which can be about any valid subnet that doesn't match the LAN's subnet). With the router's DHCP server enabled, the computer connected to the LAN side should be configured to get its address automatically.


OK, I understand what your saying now. I'm going to give it a try over the weekend. Thanks for the clarification.


Tested the Router on another system - it handles 20 MB down and 8 MB up. Will have to call Mediaclown for more info.

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