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I believe I've got the scenario outlined in this SU answer, where my 10/100Mbps router is being overwhelmed by a Gigabit switch and the devices connected to it. This comes into play with frequent website timeouts and the like... Chrome's status bar shows "Resolving host..." far more than it ever did, for example.

Here's my setup:

I have a Gigabit-capable PC (ASUS P5QL/EPU, but only connected at 100Mbps for some reason) and a Gigabit-capable Drobo 5N (which IS connected at 1000Mbps), both connected via Cat5e / Cat6 cables to a recently-installed unmanaged Gigabit switch (TP-Link TL-SG1008D), which then connects via Cat5 to my 10/100Mbps router (an ISP-supplied D-Link DSL6740U). My internet connection is 40Mbps down and 3Mbps up.

I do have the Transmission BitTorrent client running on my Drobo, which obviously generates traffic. I have limited its speeds to either 25kB/s or 40kB/s upload and 1024kB/s or unlimited download, depending on the time of day, although the slowdowns I'm troubleshooting happen all throughout the day.

Since installing the switch, I've noticed a nasty speed degradation compared to when the PC & Drobo were connected to the router directly. I only got the switch to improve file transfer speeds between my PC and the Drobo. Is the only solution to the network slowdown on my PC upgrading to a gigabit router (and appropriate cables), or is there some sort of packet configuration or MTU setting on the PC, Drobo, or router (the switch is unmanaged) that can fix things?

If I do have to upgrade the router, is there any benefit to keeping the PC and Drobo behind the switch, or should they be connected directly to the router? I imagine that retaining the switch could ease the burden on the router when I'm transferring lots of data between the PC and the Drobo, but then I also imagine that having 2 Gigabit-connected devices communicating with a Gigabit router via a single Gigabit line could cause some bottlenecking.

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  • You should not need a router with a gigabit switch integrated to achieve full performance from your rig, unless your internet connection is 1Gb down. I'd try to confirm that both router and switch are auto-negotiating correctly, and that the cable between them is healthy, and free from sources of interference. your specific hardware may exhibit some incompatability as configured. but there is no fundemental reason you can't run a gigabit lan behind a 10/100 router. I'd check the routers link speed and duplex for the uplink port, and disable jumbo frame on your clients. Nov 24, 2014 at 15:27
  • I agree with Frank here. I have a situation almost identical to yours, I installed a Gig switch so I too could increase the transfer speeds between my PC and my Drobo. I use Cat5e as well, and of course only achieve speeds of about 250 - 300 Mbps, but it is still better than 100Mbps. That aside, I do not experience any slow downs out to the web, that traffic should still run at the full speed capable of the router. One thing I might try, since this occured when you installed the switch, try removing it and see if the performance you are used to returns. If not, maybe coincidence with ISP? Nov 24, 2014 at 15:38
  • @Paperlantern, if you are getting 250-300 Mbps from a file transfer, thats actually pretty good for consumer grade Gbps equipment. generally, to get much faster, you need to focus on on the ReadWrite speed of the media on both sides of the link (for instance reading from a RAID mirror to an SSD), and most consumer grade switches can't deal with many simultaneous flows at that speed. Nov 24, 2014 at 16:19
  • @Paperlantern, I actually did just that - removed the switch from the equation - since I had to get some work done online today and couldn't handle the intermittent connectivity issues. It did indeed restore performance to pre-switch levels (Internet-wise). My concern is what was mentioned in the answer I linked to: "the hosts connected to the switch are sending it data at line speeds the switch cannot offload to the router fast enough for buffers to not overrun, and drop frames."
    – Sandwich
    Nov 24, 2014 at 19:25
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    That shouldn't be the case unless there is some Layer 2 incompatability, which is why I suggest disabling jumbo frames, and looking into the auto negotiate settings. Ethernet networks use flow control, first by buffering packets destined to cross the slower link, and by the use of Source Quench messages sent by the switch to the sending host, to ask it to slow down, when the buffers are getting full. Also, when you make an HTTP request for a webpage, you are generally only sending a few packets per http object, so its unusual to be sending much traffic to the router at all. Nov 24, 2014 at 19:32

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