Unable to achieve full ISP speed

[RosinTheBeau]

I bridged my ISP router and am currently speed testing my personal router on which I flashed OpenWRT.
The DL speed of my ISP is 400Mbps (tested and validated via the ISP router).
However, after the bridge the speed doesn't go above 270Mbps.
If I transfer files from my PC to my NAS I get good speeds of around 720Mbps. (Ethernet both sides).
I captured some network traffic with wireshark, all seems normal.
I believe the problem comes from the CPU of my personal router. While running DL tests online, the Usage tops at almost 100%

Is it normal that a 775MHz CPU tops at 270Mbps ONLY for internet connections and not in the LAN?
What do you think?

Specs:

• Router: TP-Link Archer C2 (Link here: https://www.tp-link.com/en/home-networking/wifi-router/archer-c2/)
• CPU: 775MHz, 32KiB L1d cache/64KiB L1i cache
• RAM: 58MB
• OS: OpenWrt 19.07.1
• ISP DL speed: 400Mbps
• DL speed via LAN (ethernet): 720Mbps
• DL speed via OpenWRT router: 270Mbps (fluctuating ~15%)

[pavelgl]

Try to activate Software flow offloading.

Take a look at this topic:

[SOLVED] Flow offloading in tp-link archer c7 v5 (limitation 300 Mbps on Gbps ethernet port)

hello every one, i have a tp-link archer c7 v5 and there is not the packages kmod-ipt-offload kmod-nf-flow and kmod-nft-offload be cause i want to do flow offloading (i have only 300 Mbps max on my gigabit ethernet ports....) Is there a way to have these packages, archer c7 can do NAT flow offloading ? i have this firmware : openwrt-18.06.1-ar71xx-generic-archer-c7-v5-squashfs-factory.bin kernel 4.9.120 tech data : https://openwrt.org/toh/hwdata/tp-link/tp-link_archer_c7_v5 architecture : …

I'm not sure if your router supports hw flow offloading.

[hnyman]

@RosinTheBeau

Is it normal that a 775MHz CPU tops at 270Mbps ONLY for internet connections and not in the LAN?

Yes.
The wired LAN traffic is likely handled just by the hardware switch, without CPU load.
Wan traffic requires routing, firewall, NAT, etc., so it is much more CPU intensive.

[dlakelan]

@RosinTheBeau

Is it normal that a 775MHz CPU tops at 270Mbps ONLY for internet connections and not in the LAN?
What do you think?

This is normal. The LAN connections go through the switch and don't need any cpu at all. But routing is cpu intensive. See my topic So you have 500Mbps-1Gbps fiber and need a router READ THIS FIRST

[RosinTheBeau]

Thank you all for the very prompt replies.
The Software flow offloading option worked for me. Now it's reached about 380Mbps at 77% CPU load. I am going to try to figure out if my MIPS can do hardware offloading as well.
@dlakelan I read your post and honestly it's very good. Definitely going to dig deeper into the subject.