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ZenWiFi AX XT8 - Performance tweaks

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Hey there, I’ve been tinkering with my home set up for awhile now and while I’m very happy with the results and don’t have much to complain about, I feel like I’m not quite getting the speeds I should be and would love some outside opinion.

The basic setup is a Bell Giga Hub modem/router connected to a ZenWiFi AX XT8 with a second ZenWifi AX XT8 node one floor up, on the other side of the house.

The details:

Bell Giga Hub modem/router. 1.5Gbs down, 940Mbps up
When I run a speed test from the modem itself, the plan holds true. 1.73Gbps down, 963Mbps up with a bit of variation whenever I run the test.


I have wifi disabled and have it connected to the main ZenWiFi router from the Giga Hub’s 10Gbps ethernet port to the ZenWiFi’s 2.5Gbps port via a short Cat6 cable.

Speed tests run from the ZenWiFi’s admin show nominal loss. Roughly 1.4-1.6Gbps down, 700-800Mbps up.


If I connect my computer via ethernet to the ZenWiFi (MacBook Air M1 with Anker 2.5Gbps ethernet adapter) I get a pretty solid 900+Mbsp up and down, which I imagine is as close to a theoretical max I’m going to get from a Gigabit ethernet port.

So far so good.

The ZenWiFi Node is fairly far away and using the second 5Ghz channel as its dedicated backhaul. Despite being pretty far away, it shows a solid connection and what I think are pretty good speeds, if I’m reading it right. 1360 transmit rate, 1440 receive rate.


Where things get confusing is when I connect to the second node. If I connect the same MacBook (with 2.5Gbps ethernet adapter), I get 7-800Mbps up and down. Again, that’s great, but with the PHY rates between the two nodes, I would have expected rates similar to when I was connected to the main router, or more considering on the second node, I’m using the 2.5Gbps port.

Additionally, I have a NAS plugged into the second node. It’s using 2xCat6 cables plugged into 2 regular Gigabit ports, but bonded as a single connection. I would have assumed that would also give me higher than 1Gbps rates. When I do an iPerf test between the NAS and the MacBook (using the 2.5Gpbs port), I get a Bitrate of ~940Mbps and transfer rates of ~112 MBps. This is only a tiny bit faster than when I use a regular Gigabit ethernet adapter.


So… questions:
  1. Are my expectations realistic?
  2. Is there anything I can do to reduce the drop from modem to primary router node even more?
  3. Is there anything I can do to squeeze more out of the second node?
  4. When using the 2.5Gbps WAN port on the second ZenWiFi node, does it operate at 1Gb or 2.5Gbps?
Thanks in advance for any insight!

PS When I connect the MacBook directly to the 10Gbps port on the modem, I get 1.6Gbps down and 900+Mbps up so I know my ethernet adapter is working properly.
- built-in Asuswrt speed test may not be accurate, it's CPU limited
- PHY rate is not equal to throughput, what you see is normal and expected
- link aggregation between your node and NAS is perhaps not working
- even if it was working, single connections through link aggregation are limited to single interface speed

Your system is working well, don't try to break it. XT8 can be temperamental when disturbed. It also has quite weak hardware and TrendMicro firmware features may drop the performance significantly.
Thanks for the speedy reply!

Fair point on the speed test and good to know re: PHY rate vs throughput.

As for link aggregation, that's very helpful. Now that I've dug into it a bit more, I think I was not quite understanding how it works... or at least the benefits it provides. I guess I should be doing multiple tests from different clients in parallel to see if it's working.
This link aggregation must be enabled on your XT8 as well, but the node has no GUI. What you see on the NAS side only perhaps does nothing in performance improvement. Test it and see if there is any difference between single and dual Ethernet links.
Oh, I didn't set it on the node. I set it on the NAS.View attachment 53613
Your bonded connection does not improve bandwidth the way it is set up but improves reliability. You have but one IP address for both ports. Also, the jumbo frames may not be the way to go as the packets will get fragmented once past the router and splitting and assembling packets takes a lot of resources. I use bonded connection on my DS220+ but one cable goes to the router and the other to a switch.
with the PHY rates between the two nodes, I would have expected rates similar to when I was connected to the main router, or more considering on the second node, I’m using the 2.5Gbps port.
The wireless link rates aren't static. Whatever you see when you check them is merely a snapshot of that moment in time. They constantly fluctuate at least some.

Also don't forget that unlike a full duplex connection (think of a phone call where both parties can talk / listen simultaneously), wireless as we use it is half duplex so only one side can talk at a time and the other has to shut up and listen (ever have a pair of walky talkies?). Even with a "one-way" flow of data, like copying a large file, there will be many little returns of acknowledgement, for which the file source must cease sending in order to hear them.

The XT8s may have relatively weak hardware, in the big picture, but for what they're typically called on to do, well, I quite enjoy mine.
Thanks, everyone. Sounds like I'm already squeezing everything I can out of the setup. Given that I rarely have more than one machine hitting the NAS at once, the link aggregation likely isn't doing much.

@bbunge I didn't specifically set Jumbo Frames to be on, but I do have a manually set MTU value of 9000 that maybe triggered that. I'll play with those settings and see if anything changes.

@glens you're right. Link aggregation seems to only be supported for dual WAN on the XT8. And good to know re: full/half duplex. Thanks!
I don't remember the XT8 implementation of dual WAN being /aggregational/. Are you sure it's not merely either/or?
I don't remember any Asus router with Dual WAN working properly. The reason scripts like the one below exist and the reason some folks with Dual WAN requirements use business class routers.

I'm about a week away from having the exact setup you are talking about. Did you connect to the Giga Hub using PPPoE or did you simply turn off wifi and are in a Double Nat situation? I've read you can't put the Giga Hub in Bridge mode and that there are only a few ways to get around it. PPPoE being the most popular it seems.
I'm about a week away from having the exact setup you are talking about

Then you have about a week time to rethink your XT8 purchase. Read around SNB Forums - this is one of the models with most issues reported. Weak overpriced hardware with one 5GHz 4x4 radio for wireless backhaul and one 5GHz 2x2 radio for clients + ton of firmware and connectivity issues. Not to mention it's already almost 4-years old (release date Jan 2020), mix of V1 and V2 revisions with XT9 newer version.
Make that "moderate" hardware instead of "weak" and all the radios are sufficient-to-good. Last few times I looked they were consistently selling in the lower $300 range, so considering the amount of hardware in the kit, they really don't qualify as "overpriced" either. Actually, they're quite a good value for folks who don't want or need the top of the pyramid, as well being totally unobtrusive in appearance. The only thing they /really/ lack is a 2.5Gb port on the LAN side. The second thing which could be addressed by Asus is sending a white power supply / cord instead of black, with the white version.

I don't know just how close I am to having mine for two years yet, and I sure seem to have already missed out on the problematic(?) earlier firmwares.

The XT9 has slightly better specs, mainly doing DFS on the low-5GHz radio, but are a lower-value proposition pricewise if one can live without that.
Built around BCM6755 SoC, the same in already EoL'd RT-AX56U and in one of the cheapest AX-class routers RT-AX55. This is entry-level hardware + one additional BCM43684 for wireless backhaul + some looks marketing around it. Lower $300 range now because of the age and newer XT9.
@glens I would agree. All things considered, the XT8 has served me quite well. I started this thread because I thought I was doing something wrong, but it sounds like I'm squeezing out about as much as could be expected and the Asus is performing admirably. I get rock solid signal from one end of the house to the next and speeds I shouldn't complain about.

If anything was left to be desired, I guess it would be the 2.5Gb port on the LAN side as you mentioned and access to 160Mhz channels (sounds like this is a limitation of my black, Canadian version of the XT8)... but I'm also not even sure that would work for me.

@TBONE204 I'm using the Giga Hub with wifi turned off and double NAT. So far no issues. I've had this setup for a couple of months, but the XT8 has been running pretty smoothly for me for just over 2 years now. If you can get a good deal on it, I wouldn't hesitate, but I don't have much to compare it to.
I've actually had the XT8's for about 3 years now - I meant that I will be getting the Bell Fibe 1.5GB service with the Giga Hub in about a week. my XT8's have performed pretty well for me and I currently have no issues with them. I was glad to see someone with this setup since mine will look the same by the end of the week. I'm glad it's working out for you and hoping I will have no issues either.
Good to hear it is working well for you guys. Lots of connectivity issues reported here.

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