Today at work I ran into a really long-standing issue that we’ve had in one of our company branches. This branch uses an EOL/EOS Meraki Z1 Teleworker Gateway and also uses a hilariously EOL/EOS Cisco 2801 Integrated Services Router.

The setup is very straightforward, on the Internet side of the Teleworker gateway is a Comcast cable modem, and it’s only capable of 60mbit downlink and 10mbit uplink for maximum speed. We rebooted everything, re-tested from the cable modem and then to the desktop itself, and the speed from the cable modem was just as we expected, 60/10, but the speed from the desktop was 4/6!

I had rebooted everything. The cable modem, the Meraki Z1 Gateway, the Cisco 2801 ISR, and the Cisco 3560 Catalyst switch. Even the Cisco IP Phone got a reset! The speed gremlin held out, 4/6. So while working with some staff in the branch, I just happened to mouse-over the graphic on the Meraki Dashboard for this device and spotted the gremlin. The mouse-over tip for LAN1, where the Cat5 cable goes from the Meraki Z1 to the Cisco 2801 showed 100mbit/half-duplex. I checked into the terminal on the 2801 and verified that the port was fixed at 100mbit/full-duplex! So, I opened the Meraki Z1 device Ethernet configuration page, found LAN1, and changed it from “Auto” to 100mbit/full-duplex.

Forcing the speed and duplex settings resolved all the problems right out to the Desktop! Hooray! And what I learned from this is that Meraki Z1 Teleworker Gateways cannot successfully auto-negotiate link speed and duplex with a Cisco 2801 Router. So if you have unexplained crappy network performance, always make sure that link speed and duplex match what you think they should. Sometimes “Auto” isn’t.

Photo Credit: Gremlin Grotesque, Winchelsea church
cc-by-sa/2.0 - © Julian P Guffogg - geograph.org.uk/p/3334405