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I work in a very small office where we have approximately 5 office desktops wired to the internet through what appears to be CAT5 mixed with CAT5e wiring.

The wires flow in this order: Desktops > Server room Patch panel > Netgear 24port gb switch > Cisco router 1900 series > Netgear 8port gb switch > Modem

We switched to a new ISP recently in order to get fast cable internet (300 Mb/s down). However, speed tests on the desktops yield only 7-10 Mb/s.

Plugging into the modem directly (or the 8port switch in front of the modem) yields high speed (280 Mb/s). Plugging directly into the 24port switch yields the slow desktop speeds pointing to either that device (or more likely, the Cisco router) as being an issue.

What are some of the best troubleshooting steps I can take to solve this issue? Are there any obvious configuration issues that a Cisco router could have to cause this kind of speed barrier?

I appreciate any advice. Thank you.

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    How are the interfaces on the Cisco router and Netgear switch configured for speed and duplex? Why do you have an 8 port switch between the router and the modem?
    – joeqwerty
    Aug 31, 2016 at 15:38

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The Cisco router is probably hard-coded to a 10Mbps link speed on its internet-facing interface.

It's worth checking that. Do you have access to the Cisco router and its configuration? That would tell you for sure.

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  • Check the settings and error counters on the interfaces on the 24 port switch (see if it has a web UI that will show this)

  • Connect a workstation directly to the LAN side of the Cisco and retest performance (eliminates 24 port switch and its handoff to Cisco from situation)

  • Log into the Cisco and...

    • look for indications of unexpected port speed (e.g. 10 vs 100 or 1000) or duplex (e.g. half).
    • look at the interface configuration connected to the internal switch. Is it by chance forced to a static configuration in regards to speed and/or duplex? (If so, since the switch probably isn't, the switch will fail to auto-negotiate and fall back to low performance and, possibly a mismatch which will causes lots of errors)

Also, beware that the 1900 series may not have appropriate performance for a 300M ISP link. Though the specific performance you'll get out of it will vary by features in use and overall configuration. A bit more details here: https://supportforums.cisco.com/sites/default/files/attachments/discussion/white_paper_c11_595485_10.pdf

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