Slow CRS326 connection to internet

Hi, i repost this problem with additional data/information and attach the config.

My current setup as follow :
I have 2 devices from ISP : a modem and wifi router (Let’s name this router as router A)
I have my own wifi router. Let’s name it router B.
Router A is on 1st floor. Router B is on 2nd floor.
Internet —> ISP modem —> ISP wifi router (router A) —> all devices { wireless router B, server, PC, laptop , handphone etc }

I bought a mikrotik switch CRS326 https://mikrotik.com/product/CRS326-24G-2SplusRM

I have 2 scenarios :

Scenario A : connect the CRS326 to router A
Internet → ISP modem → router A → CRS326 – > all devices.
In this scenario, Internet works as expected. No problem.

Scenario B : connect the CRS326 directly to ISP modem
Internet → ISP modem → CRS326 → all devices
So now , the router A is behind the CRS326 and use the router functionality of CRS326 to act as master router.
The Problem : internet connection drop about 1/10 . For example when browsing youtube, normally i can load the page in a split second but now it takes more than 1 minutes to load the page and most the time the video will not play.
I’m aware that CRS326 is not a router, it’s a switch but it has the router functionality with routerOS. But there won’t be heavy routing jobs , i use this CRS326 mostly only for LAN traffic. For example : i have 5 PC for editing and want to access data on local server. The need to access the internet only for browsing. Anyway in this test, i only use 1 laptop , no other load , so that severe slowness didn’t make sense.

I didn’t use any fancy setup, just very basic setup. When i switch the cable to Scenario A, the speed goes back to normal again, but every time i switch to Scenario B, it always back to become very slow. I don’t understand why this happen, setting are just the same.

The problem solved if i use scenario A. But I want to implement scenario B , can someone spot what is wrong or what cause the slowness ?

Also later, i plan to add 2nd ISP so then both ISP will be connected to my CRS326 and want to use load balance to get higher overall upload speed.

I exported the config and attached them in this post. there 2 attachment ( NORMAL : setting i use in scenario A and SLOW : setting i use in scenario B/slow problem )
slow.rsc (2.43 KB)
normal.rsc (2.43 KB)

What kind of ISP-Speed’s are we dealing with ?
50 Mbits, 100 Mbits, 150 Mbits, 1000 Mbits ?

Concur with Conny, if the thinking is the connection is 300Mbps or less, have the CR326 do everything (routing and switching), otherwise if higher like 1gig,
then the approach would be different.

To add to @anav Post ,

The 300Mbits would be for the combined Speeds of ISP1 and ISP2

CRS326 can handle a speed of approximately 269.9 Mbps in Routing Mode …

https://mikrotik.com/product/CRS326-24G-2SplusRM#fndtn-testresults

from ISP = 100mbps. realistically i get 85-90Mbps.

The test i did using 100Mbps from ISP. Anyway, with no other load , if i open any website and it took minutes to load, it doesn’t make sense.

my internet speed is 100Mbps

so with this :
isp modem–>isp router–>crs326 -->mylaptop
i got normal speed.

but if i connect CRS326 directly to ISP modem ( not using ISP router )
isp modem–>crs326–>mylaptop
got very slow response.

in this test, i’m only use my laptop, no other devices are connected (just to make sure no other load)

Soo, Took a second look at your RouterOS-Config…
Found the Problem in the Mikrotik Wiki (https://wiki.mikrotik.com/wiki/Manual:CRS3xx_series_switches)

Currently it is possible to create only one bridge with hardware offloading on CRS3xx series devices

and you have 3 Bridges active…

Posible Solution :

Step 1: Disable HW-Offloading on WAN-bridge
Step 2: Only have 1 bridge for “LAN” and “Server” and Activate HW-Offloading
Step 3: Use VLAN to segregate your Networks