[SOLVED] Abysmal speeds in a Realtek RTL8380M switch (ZyXEL GS1900-8HP v2)

Hello. I have a (Realtek RTL8380M) ZyXEL GS1900-8HP v2 with OpenWrt 21.02.3 r16554-1d4dea6d4f. It's connected to a NanoPi R4S with OpenWrt SNAPSHOT r20152-a3e4949998. I've just finished setting everything up but I get very low speeds when connected to the switch (around 20Mbps when I have 1Gbps). It's definitely the switch because when connecting directly to the R4S I get full speed. I've enabled packet steering but I'm unable to find anything related to flow offloading and whatnot. Any help is appreciated.

Any errors you are seeing? Link speeds reporting anything off?

Switching is done in hardware, so unless you set up some kind of NATing or routing on your GS1900-8HP v2, you should be seeing near wirespeeds.

Link speeds are reported as 1Gbit full duplex. I can't see anything weird in the kernel log (https://pastebin.com/upFxb8fS).

Are you using the XyZEL purely as a switch, or is it routing? The routing performance would probably be terrible, but it should be fast as a switch.

I don't think so, at least that's my intention, but perhaps I messed something up in my configuration. I have a DHCP server on my LAN side and a firewall in both LAN and WAN interfaces. Perhaps that's what tanking speeds? Sorry for my inexperience.

I'm sorry, I don't understand your response -- the language is too vague.

What is your intention? To use it as a router or only as a switch? Do you have another router that will remain in place (i.e. internet > R4s > switch)?

What device has the DHCP and firewall configured? Have you made changes relative to the default? (the default configuration is usually sufficient, the LAN typically operates as if it doesn't have a firewall, which is often the right approach for home users).

Oops, sorry about my vagueness. I just want to extend the LAN side of my R4S with the switch. I just want the switch to distribute WAN connection from the router and perhaps segregate my LAN into different untagged VLANs. The switch has a WAN with a DHCP client and a LAN with a DHCP server. Both interfaces have an active firewall. Thanks for the help.

Actually, the router (the R4S) is responsible for "distributing" the WAN connection.

VLAN routing should be handled by your main router. The switch should only be responsible for switching -- in this case, making the each of the ports members of the desired VLAN, and handling the trunk connection that goes up to your R4S.

This is why the performance is terrible. Your switch should not be routing, and you shouldn't be running a firewall here. It should all happen on the R4S. The hardware inside your switch is designed for fast switching, but it cannot route traffic nearly as fast.


Yep, that was it. Everything works fine now. After doing a bit of reading I began to understand it (OpenWrt as a wire-to-wire switch). Thanks for you thorough explanation.

Great! Glad it helped!!

Allow me to quote myself, eh :innocent:. First reply :wink:.

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