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So I have this ADSL modem/router issued by the ISP and I reconfigured it to bridge mode. ISP method for acquiring internet access is plain DHCP. The device has 1 telephone jack connected to the Internet and four (4) Ethernet ports, and is also Wi-Fi capable.

Since it is now in bridge mode, the end devices plugged in to the Ethernet ports (or the once logged in to the Wi-Fi connection) now all get public internet IPs.

In the router mode, I can notice that bandwidth download speed is divided among all the devices connected to the router. Subscription speed is 3Mbps.

I already have a better grade Linksys router, so I plugged this into 1 Ethernet port on the bridge and also disabled the Wi-Fi on the bridge.

So, I haven’t really bothered to test if it’s the same behavior in bridge mode.

Do each device get separate 3Mbps max speed because they’re with their own public IPs? Or is the bandwidth limit tied to the physical device—the modem—itself??

  • Please update your question once you have tested bridge mode – Ramhound Oct 19 '15 at 17:05
  • I'm a bit wary in testing this. I don't want to get unwanted attention from my ISP...lol. – Poly Bug Oct 19 '15 at 17:07
  • The combination of this statement "Since it is now in bridge mode, the end devices plugged in to the ethernet ports (or the once logged in to the wifi connection) now all get public internet ips." and this statement "I haven't really bothered to test if it's the same behavior in bridge mode" makes what you have said really confusing. – Ramhound Oct 19 '15 at 17:12
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    The bandwidth limitation almost certainly comes from the ADSL link. – David Schwartz Oct 19 '15 at 17:18
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    @PolyBug I'm talking about the actual link speed, not QoS. ISPs offer different ADSL packages on the same type of link by changing the physical link speed. For example, I have a VDSL link with a maximum attainable upload speed of 11.48Mbps and a maximum attainable download speed of 61.1Mbps, but the link is actually running at 27.6Mbps down and 3.0Mbps up, because that's what my provider limits it to. – David Schwartz Oct 19 '15 at 17:31
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The 3Mbps speed limit is normally enforced by using different physical-level signalling. E.g. the signals on the ADSL connection operate at different frequencies: usually when your modem connects to your ISP it'll try to synchronize using various protocols and choose the actual signalling speed based on the quality of the connection (the amount of noise, for example). This choice is often additionally controlled by settings on your ISP's side. So the ISP can choose which physical protocol is used and which frequency is selected with that protocol. This is not only useful to impose a max bandwidth limit according to your contract, but also to override the auto-negotiation (which may sometimes choose a speed that's too optimistic leading to frequent disconnections).

So all the protocols on top of that (e.g. IP) will have to live within the physical constraint of the ADSL-level protocol used. IOW, no matter how many different IPs you gt and machines you connect you shouldn't be able to extract more than the 3Mbps transfer limit.

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