- I just moved over to a Linksys EA8100 OpenWrt from a DIR-868L FreshTomato 2024.12
- On my FreshTomato, I allowed MTU of 9270 and usually hit ~900Mbps on my 1G fibre
- But I'm only getting ~600Mbps with OpenWrt
- I tried increasing my WAN MTU, but it could only go til 9200 and it dropped the speedtest down to below 100Mbps
- Of course, 600Mbps is still decent, but my aim is to configure OpenWrt optimally
- Any idea what I'm doing wrong?
What does your ISP specify as your interface frame size?
Internationally, it's generally 1500 without special arrangements.
It can happen when your device has to constantly chop a 9200 frame to 1500.
If this is the device I helped you with previously, have you enabled Software/Hardware Flow Offloading to get full 1 Gbps speed from the hardware?
Look on the web GUI on the main firewall page.
- I don't know what my ISP specified, but I knew it was 900 vs 600Mbps with/without jumbo frames (9270 bytes) on FreshTomato
- Yes, both offloading already enabled
Well only your ISP can change that.
Wow. So what was the speedtest result when disabled?
And to be clear, this traffic isn't physically on the trunk port we created before, correct?
Do you mean nothing I do will affect the speed? Because I'm quite certain about the effect in FreshTomato with/without jumbo frames.
When offloading is disabled, the speed is about the same, however, I did not check on the router CPU, there could be a difference here.
And yes, I removed the trunked settings I made earlier to try and isolate this jumbo frames, so those settings are now gone.
The DIR-868 being ARM instead of MIPS had more CPU power. The MT7621 you're running now isn't really enough for gigabit ISP. MTU has nothing to do with this.
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make sure you enable hw offloading, no matter what.
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And I thought this EA8100 was an upgrade 
I ought to check my CPU to confirm then, right?
Shouldn't be a problem.
mt7621 doesn't support jumbo frames. Return default mtu, enable hw offload and check cpu usage.
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