Hi,
I got FTTH - Fiber to my home with 1GB/s up and down speed.
As I wanted to build a home network I bought the MikroTik CRS309-1G-8S-IN and connected SFP+1 port (SFP-10G-T) with the Fiber router. I activated RouterOS but did only the pure basic setup (Interface, all ports Bridged, DNS, DHCP).

I'm facing a wired performance problem. Having my PC directly connected via an ethernet cable I have almost the max 1GB up and down speed. But when going via CRS309 I only have max one third (300MB/s) up and down speed.
Independent of using an 1GB ethernet SFP interface (SFP-GB-GE-T) or a 1GB SFP Fiber (SFP-GE-BX) via media converter.

I'm currently only using 2 ports, my PC and a Notebook so that should not overload the CPU or traffic... Also on the Notebook speed is the same slow one.

Do you have any idea what could be the problem or how to troubleshoot this? I'm a newby with MikroTik and routers.

Thanks for your help.

Try it (internet connection with ISP) with a straight ethernet port on the CRS, which would quickly point to the SFP port as the issue.........

If it's only used for switching it should not be hitting the CPU at all. If you get high CPU during the tests, then you have a configuration issue and you should post an export of your config.

If you are using it for routing, well, this might be the best you will get as this is primarily a switch with limited routing capabilities.

If there is not high CPU, then I would say it's an issue with ingress/egress rates when going from 10g to 1g, but you don't mention 10g anywhere.

I highly suggest posting an export.

Thanks @anav, @biomesh

CPU in normal behavior using the internet causes very low CPU load <10% even streaming videos but with only 300MB.

SFP+ Port1 is configured as "IN"-Port / WAN connected to the ISP router using a 10G transceiver "SFP-10G-T" to have the possibility to update somewhen in the future when maybe my ISP provides 10G.
I would be confused if it's a 10G to 1G issue as I have exactly the same behavior using a 1G SFP transceiver "SFP-GB-GE-T" in SFP+ Port1 instead of the 10G transceiver.

Here the export - hope this brings some clarity. Appreciate your help:
# dec/30/2021 15:20:17 by RouterOS 7.1.1
# software id = 0QAH-AZR1
#
# model = CRS309-1G-8S+
# serial number = #######
/interface bridge
add admin-mac=######### auto-mac=no comment=defconf name=bridge
/interface ethernet
set [ find default-name=ether1 ] advertise="10M-half,10M-full,100M-half,100M-f\
ull,1000M-half,1000M-full,10000M-full,2500M-full,5000M-full"
set [ find default-name=sfp-sfpplus1 ] advertise="10M-half,10M-full,100M-half,\
100M-full,1000M-half,1000M-full,10000M-full,2500M-full,5000M-full" name=\
sfp-sfpplus1-ether-10G
set [ find default-name=sfp-sfpplus2 ] advertise="10M-half,10M-full,100M-half,\
100M-full,1000M-half,1000M-full,10000M-full,2500M-full,5000M-full" \
auto-negotiation=no name=sfp-sfpplus2-fiber-LCAPCSM-1G
set [ find default-name=sfp-sfpplus3 ] auto-negotiation=no name=\
sfp-sfpplus3-ether-1G
set [ find default-name=sfp-sfpplus4 ] disabled=yes
set [ find default-name=sfp-sfpplus5 ] advertise="10M-half,10M-full,100M-half,\
100M-full,1000M-half,1000M-full,10000M-full,2500M-full,5000M-full" \
auto-negotiation=no name=sfp-sfpplus5-ether-1G
set [ find default-name=sfp-sfpplus6 ] auto-negotiation=no disabled=yes
set [ find default-name=sfp-sfpplus7 ] disabled=yes
set [ find default-name=sfp-sfpplus8 ] advertise="10M-half,10M-full,100M-half,\
100M-full,1000M-half,1000M-full,10000M-full,2500M-full,5000M-full" \
auto-negotiation=no name=sfp-sfpplus8-fiber-LCUPCMM-1G
/interface list
add name=WAN
add name=LAN
/interface lte apn
set [ find default=yes ] ip-type=ipv4
/interface wireless security-profiles
set [ find default=yes ] supplicant-identity=MikroTik
/ip dhcp-server
add interface=bridge name=dhcp2 relay=192.168.88.1
/ip pool
add name=dhcp ranges=192.168.88.100-192.168.88.254
/ip dhcp-server
add address-pool=dhcp interface=bridge name=dhcp1
/port
set 0 name=serial0
/interface bridge port
add bridge=bridge comment=defconf ingress-filtering=no interface=ether1
add bridge=bridge comment=defconf disabled=yes ingress-filtering=no \
interface=sfp-sfpplus1-ether-10G
add bridge=bridge comment=defconf ingress-filtering=no interface=\
sfp-sfpplus2-fiber-LCAPCSM-1G
add bridge=bridge comment=defconf ingress-filtering=no interface=\
sfp-sfpplus3-ether-1G
add bridge=bridge comment=defconf ingress-filtering=no interface=sfp-sfpplus4
add bridge=bridge comment=defconf ingress-filtering=no interface=\
sfp-sfpplus5-ether-1G
add bridge=bridge comment=defconf ingress-filtering=no interface=sfp-sfpplus6
add bridge=bridge comment=defconf ingress-filtering=no interface=sfp-sfpplus7
add bridge=bridge comment=defconf ingress-filtering=no interface=\
sfp-sfpplus8-fiber-LCUPCMM-1G
/ip settings
set max-neighbor-entries=8192
/ipv6 settings
set disable-ipv6=yes
/interface list member
add interface=sfp-sfpplus2-fiber-LCAPCSM-1G list=LAN
add interface=sfp-sfpplus3-ether-1G list=LAN
add interface=sfp-sfpplus4 list=LAN
add interface=sfp-sfpplus5-ether-1G list=LAN
add interface=sfp-sfpplus6 list=LAN
add interface=sfp-sfpplus7 list=LAN
add interface=sfp-sfpplus8-fiber-LCUPCMM-1G list=LAN
add interface=sfp-sfpplus1-ether-10G list=WAN
add interface=bridge list=LAN
/ip address
add address=192.168.88.1/24 interface=bridge network=192.168.88.0
add address=192.168.1.100/24 interface=sfp-sfpplus1-ether-10G network=\
192.168.1.0
/ip dhcp-client
add disabled=yes interface=sfp-sfpplus1-ether-10G
/ip dhcp-server network
add address=192.168.88.0/24 gateway=192.168.88.1 netmask=24
/ip dns
set servers=1.1.1.1,1.0.0.1,8.8.8.8,8.8.4.4
/ip firewall filter
add action=fasttrack-connection chain=forward comment=\
"FastTrack DNS connection for TCP to make Internet/DNS faster" dst-port=\
53 hw-offload=yes protocol=tcp
add action=fasttrack-connection chain=forward comment=\
"FastTrack DNS connection for UDP to make Internet/DNS faster" dst-port=\
53 hw-offload=yes protocol=udp
/ip firewall nat
add action=masquerade chain=srcnat out-interface-list=WAN
/ip route
add disabled=no dst-address=0.0.0.0/0 gateway=192.168.1.1
/ip service
set ftp disabled=yes
set api disabled=yes
set api-ssl disabled=yes
/system clock
set time-zone-name=Europe/Zurich
/system routerboard settings
set boot-os=router-os
/system swos
set allow-from-ports=p1,p2,p3,p4,p5,p6,p7,p8,p9 identity=MikroTik
/tool graphing interface
add

You are using it as a router, generally not a good idea for a switch. You might get better performance using the l3hw offloading on this device with ros 7 (which you are using)

https://help.mikrotik.com/docs/display/ ... Offloading

great!
Tried some of the Offloading configurations.
Layer 3 Hardware Offloading did not work properly or didn't change something, not even enabling it port by port.

But adding Fasttrack connections to the firewall rules brought the full speed!
Offloading Fasttrack Connections
/ip/firewall/filter
add action=fasttrack-connection chain=forward connection-state=established,related hw-offload=yes protocol=tcp
add action=fasttrack-connection chain=forward connection-state=established,related hw-offload=no
add action=accept chain=forward connection-state=established,related

Can I leave this rules or do you see a problem?
Didn't change other settings, just the firewall rules and I have now equal speed via the CRS as directly via IPS router.