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XT8 in media bridge mode: WAN port slower than LAN port?

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tgl

Very Senior Member
I just got done tracing through a weird performance problem, which boils down to $SUBJECT. I have a pair of XT8s, one in AP mode connected to my wired net, one in media bridge mode. If I plug a device into the bridge's LAN1 port, I can get pretty nearly wire-speed iperf3 results to a server on the wired net: 910Mbps download, 920Mbps upload, zero retries. Plugging the same device into the bridge's WAN port, I get 477Mbps download (with 139 retries in a 10-second run), 920Mbps upload. What the heck? I'd think it was some compatibility problem between the XT8's 2.5G WAN port and my 2.5G Ugreen USB/ethernet dongle, except I get similarly awful results from a different 2.5G device plugged into the WAN port.

Anybody seen the like? Both XT8s are running firmware 388.22525. I don't think the wireless link is a factor: the bridge is reporting RSSI typically -42dBm and link rate usually 1801Mbps, and they are running in U-NII-4 spectrum (channel 169, 80MHz bandwidth) which I'm pretty sure is still reasonably-clear airspace in my neighborhood.
 
I just got done tracing through a weird performance problem, which boils down to $SUBJECT. I have a pair of XT8s, one in AP mode connected to my wired net, one in media bridge mode. If I plug a device into the bridge's LAN1 port, I can get pretty nearly wire-speed iperf3 results to a server on the wired net: 910Mbps download, 920Mbps upload, zero retries. Plugging the same device into the bridge's WAN port, I get 477Mbps download (with 139 retries in a 10-second run), 920Mbps upload. What the heck? I'd think it was some compatibility problem between the XT8's 2.5G WAN port and my 2.5G Ugreen USB/ethernet dongle, except I get similarly awful results from a different 2.5G device plugged into the WAN port.

Anybody seen the like? Both XT8s are running firmware 388.22525. I don't think the wireless link is a factor: the bridge is reporting RSSI typically -42dBm and link rate usually 1801Mbps, and they are running in U-NII-4 spectrum (channel 169, 80MHz bandwidth) which I'm pretty sure is still reasonably-clear airspace in my neighborhood.

Not much I can say that I'm sure you haven't already tried. Did you check to see if the limitation is CPU (hitting 100%)? Might narrow it down somewhat. Probably some design flaw, they do some odd stuff with the WAN ports on some of the routers to separate them from LAN, and maybe that isn't totally stripped off when it is put in bridge mode.
 
Did you check to see if the limitation is CPU (hitting 100%)?
Interesting idea, but no cigar --- as far as I can tell from the admin GUI display, the CPU load is pretty nominal (one core at about 15%, rest nothing) and there isn't much difference in it between transfers through the WAN port and the LAN ports.
 
Interesting idea, but no cigar --- as far as I can tell from the admin GUI display, the CPU load is pretty nominal (one core at about 15%, rest nothing) and there isn't much difference in it between transfers through the WAN port and the LAN ports.

Gotta be something with the architecture and the way they're implementing the WAN port. May have to go for a $15 switch to hang off the LAN :)
 

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