[Solved] Fritzbox 7530 external modem pppoe speed (Custom firware)

Hi at all,

The Background:
I have recently changed my ISP. The new one offers FTTH and provides an external modem. i also received a Fritzbox 7530. It now runs a customized OpenWrt which was build from OpenWrt version 19.07.7. To connect the internet i am configuring the switch the way that one of the LAN ports gets tagged with the necessary VLAN (700) and maps to the internal wan interface using the pppoe protocol.

The Question:
The general internet access works fine so far but I am expecting a throughput as contracted of up to 500 Mbit/s which i achieved via using the stock firmware of the router but not with OpenWrt. I am capped at somewhere between 50 Mbit/s and 70 Mbit/s (downstream). Also i had a look at the CPU usage via htop while the speedtest was running. Turns out that none of the 4 cores is fully utilized. Ping timings are slightly worse as well.

Is this a know issue or am i missing a certain configuration? Any suggestions are well appreciated !

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ipq40xx feels a bit marginal for that kind of WAN speed/ connectivity. Using plain ethernet/ dhcp, I've seen it achieve around 375 MBit/s, with software flow-offloading enabled I can achieve my contractual limits of ~430 MBit/s - while I can't say how much faster it could go, I don't think there's much of a margin left. Now PPPoE is a considerable burden for the CPU, which would impact the throughput as well - but it should still do (a lot-) more than 70 MBit/s.

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That specific router was given to me by the ISP when getting the contract. I also used an Archer C7 in its place before which provided about the same speeds but had its CPU maxed out. So I wanted to use the Fritzbox which performed decently with the stock Firmware.

I tried out to check Software flow offloading and it seems to have a better distribution of work across the cores. But sadly that was not the issue to begin with. Still thanks for the tip.
I guess for the same reason pppoe at least is not the bottle neck.

Furthermore I came across the whole discussion about enabling the usage of the routers Modem. But since i am using an external one that as well seems to not be helpful.

Any other things i can try?

The switch tab should show 1000baseT full duplex for the LAN ports you connect the client and modem to. Over WiFi you should use at least 867MBit at 5 GHz (shown on overview or wireless).
Also I always install luci-proto-ppp and luci-proto-ipv6 packages. My ZyXEL NBG6617 (IPQ4xxx) easily maxes out my 100 MBit FTTH connection. Modem is Huawei Echolife hg8010u.

I do confirm the 1000baseT full duplex. Wifi is about 114 Mbit/s which i relate to the distance. I checked with a wired connection too which obviously improved the speed slightly to about 110 Mbit/s. luci-proto-ppp and luci-proto-ipv6 are installed already.

How fast is the official 19.07.7 build in comparison?

took me a bit but i checked with OpenWrt stock firmware and yes... it is faster. But it still caps at 300 Mbit/s which is about 200 Mbit/s below expected but a great great improvement anyway.

Flow offloading actually has a negative effect now and reduces the downstream to about 200 Mbit/s.
Ping timings also slightly improved.

CPU still not fully saturated but at least i see my little one working hard.
As far as the initial question is concerned i would call that solved and I will contact the developers of the custom firmware

Thx Guys


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