Let me just say I am by no means a networking expert. I’m just a troubleshooter. If I use the wrong approach or terminology, please feel free to point me in the right direction.
My company has 3 sites all using Meraki MX devices. Connected over VPN. Let’s call them A, B, and C.
Sites A and B are in the same town. Transfer speeds seem fine.
Site C is about 130 miles away. we cannot get our data transfer speeds above an average of 15-20Mpbs. Both sites A and C have symmetrical Gigabet internet. all internet speed tests are fine.
All servers are at Site A and all sites use ERP software that communicates to SQL at Site A.
I did a packet capture at Site C of a speed test sending 1 megabyte of data to and from the data collection folder. (Granted it was also showing whatever other traffic was happening between my computer and the server in that couple seconds as well) It shows that there is a lot of fragmentation on the sending but none on the receiving. Like thousands of instances of fragmentation.
According to support the default MTU on all the Merakis is 1500. The Tunnel MTU IS 1400 and the packets were fragmenting at 1386. I pinged the server and told it not to fragment, hoping to find the biggest acceptable MTU. This returned a result of 1344 was the biggest the server would take without fragmenting.
I lowered my Ethernet MTU to 1344 and did another packet capture. Running the same test of reading and writing 1 megabyte to the data collector. Now the packet fragments at a lower number. Still seemingly thousands of instances of fragmentation. I also did a tracert and pinged all the hops between me and server (12 hops) with -f and gradually found their fragmentation points as well. Some were lower than 1344.
I should also note that I brought the Site C Meraki to my home about 20 miles from C and tested it on a completely different ISP, also with gigabit speed. No difference.
can anyone suggest the next step? I just started with this company and I would basically be a god among men if we could solve this. (Not really but it would feel really good to solve this for them.)
Hello and thank you for taking time to reply. I did try a wide variety of MTU settings on the ethernet port with the same results.
We ended up RMAing the site C just to see if it was a hardware issue (it wasn't) and we havent returned it yet so I currently have a spare at home I am tinkering with so as to not disrupt anything at the office. Ive rebooted it multiple times.
Yes we only run stable firmware.
I have enabled timestamps on noth end with no effect.