Weird Issue - No download speed but correct upload speed

Liquid_Entity · 1 May 2020 at 11:38

Hi

It doesn't seem like my network team have any idea what is causing the issue so I am coming to the right gurus.

We have a 20Mbps/20Mbps fibre connection and through random times in the day the download drops to near 0MBps but upload is not affected. There is 1 server (Dell PowerEdge R630) and 16 clients (Dell 9020 PCs) on 1Gb network (unmanaged switch) going in to a Cisco 887 DSL Router.

The ISP say they can't find any reason for the issues and the utilisation graphs don't correlate with the issues we're seeing.

Does anyone have any other idea what could be causing it?

Caged · 1 May 2020 at 12:14

Are you monitoring the reachability of any internet destinations and/or monitoring the reachability of your site from internet locations?

It might be worth getting a RIPE Atlas probe and using your account to set up inbound ping monitors which will show you if the drops can be observed, and once that happens you can move on to getting traceroutes to pass to your ISP.

Liquid_Entity · 1 May 2020 at 12:49

I have no idea what you just said.

Janesy B · 3 May 2020 at 19:34

Last time I saw something like this I had a port on half duplex because one side of the link was forced and the other was on auto so maybe worth checking that. Upload was fine but only got about 0.1mbps download.

do 'clear counters' on enable mode and then see if you get any CRCs/input errors incrementing on any ports, 'show int status' will show you the port negotiation on the router.

Might be worth ruling out the unmanaged switch by patching in a client to one of the switchports on the back of the router if you can as well. If you want to share the cisco config and an output of shot interfaces (removing anything sensitive) I'd be happy to take a look. I've been looking after 891s and 881s which aren't too dissimilar.