Deco P9 + Super Hub 4 Setup

spenncerr · 2 Dec 2021 at 21:11

Dunno if this is the right place for this but.. I've got a Deco P9 mesh system connected to my new SH4.

I've upgraded to 1gig from VM during the summer this year and I'm getting great speeds connected directly to my SH4 in modem mode.

Connecting my Deco P9 to the SH4 and then connecting a PC via ethernet to the P9.. the speed drops dramatically by around 90% - have I set something up wrong? Why is the ethernet speed connected to my Deco P9 so slow? WiFi not much better?

Connected directly to my SH4 with a cat6 cable and I get full 1gig speed. Adding in the P9 device between my PC and SH4 I get 88Mbp/s on the same cat6 cable connected to the P9?

Thanks.

WJA96 · 3 Dec 2021 at 07:18

Assuming a 5GHz AC connection and 867Mbps claimed max data simplex transfer speed then half of that gives you the maximum duplex speed (the one you’re measuring) of 433Mbps which is then split 50/50 between the mesh function and the client so the absolute theoretical maximum you could ever expect from the Deco P9 (even wired through the gigabit port)would be 215Mbps and you’re getting half that. It doesn’t seem unreasonable if you’re in a congested WiFi zone.

the-evaluator · 3 Dec 2021 at 07:49

So the connection is something like this:

SH4--Deco P9--PC

Are the dashled lines all ethernet cables? I'm trying to work out if the Wi-Fi backhaul on the P9 is even used or if you're connecting everything by cable.

When you say the speed drops by 90%, I'm guessing that equates to around 100Mbps? If so and my assumption about the physical connection is correct you likely have a cabling problem. One of the links is sitting at 100Mbps instead of 1Gbps.

WJA96 · 3 Dec 2021 at 09:20

And I presume that you have switched off one of the routers? If not then the Deco P9 will act as a NAT'd DHCP server (which wouldn't explain the radical drop in speed, but it won't help either).

the-evaluator · 3 Dec 2021 at 09:23

WJA96 said:
And I presume that you have switched off one of the routers? If not then the Deco P9 will act as a NAT'd DHCP server (which wouldn't explain the radical drop in speed, but it won't help either).

SH4 is in modem mode so there shouldn't be any double NAT.

WJA96 · 3 Dec 2021 at 10:22

the-evaluator said:
SH4 is in modem mode so there shouldn't be any double NAT.

Fair enough. This very much looks like one of those threads that were prevalent in 2020 when BT launched the 910Mbps FTTP packages and everyone said "I'm only getting 200Mbps on my iPhone" etc. etc.

the-evaluator · 3 Dec 2021 at 10:28

WJA96 said:
Fair enough. This very much looks like one of those threads that were prevalent in 2020 when BT launched the 910Mbps FTTP packages and everyone said "I'm only getting 200Mbps on my iPhone" etc. etc.

Yeah, it's hard to tell if the OP is geting the poor performance using a fully wired connection or if there's WiFi involved. I think it's wired ethernet all the way which is why I think something is linking at 100Mbps.

WJA96 · 3 Dec 2021 at 10:30

Possibly. He does say he's using the same CAT6 cable which would imply there is either another cable or WLAN involved.

the-evaluator · 3 Dec 2021 at 10:33

WJA96 said:
Possibly. He does say he's using the same CAT6 cable which would imply there is either another cable or WLAN involved.

I read this bit as it's wired all the way:

Connecting my Deco P9 to the SH4 and then connecting a PC via ethernet to the P9.

The SH4 - Deco P9 link must be ethernet and then the PC is connected by ethernet.

Bug One · 3 Dec 2021 at 10:38

If you've got your setup as SH4-(ethernet)-Deco P9-(ethernet)-PC then I expect it's down to QOS.

Open your deco app, click on MORE down the bottom, then under HOMECARE click QoS. There's an option for Total Bandwidth in there. I expect that's still got your old internet speed. Click Edit, and get your new speed via a Speed Test.

spenncerr · 3 Dec 2021 at 14:16

Thanks all!

Yes you're all right the setup is as is: SH4-(ethernet)-Deco P9-(ethernet)-PC

Using the same cat6 cable directly to the SH4 I get full gigabit speed. Connected as above with the Deco P9 involved.. it drops 90%.

QoS has been changed to 1000 (maxed out basically) - I set that when I first ever setup the Deco units so I don't think it's that.

spenncerr · 3 Dec 2021 at 14:18

WJA96 said:
And I presume that you have switched off one of the routers? If not then the Deco P9 will act as a NAT'd DHCP server (which wouldn't explain the radical drop in speed, but it won't help either).

Do you mean the SH4? It's in modem mode, yes. So I'm only getting wireless around the house from the Deco units. But this isn't a wireless issue, it's an ethernet issue. Although wireless speeds aren't exactly great on devices even when directly next to the primary Deco P9.

spenncerr · 3 Dec 2021 at 14:19

the-evaluator said:
I read this bit as it's wired all the way:

The SH4 - Deco P9 link must be ethernet and then the PC is connected by ethernet.

Yes you're exactly right. Which is why I don't understand why I'm having this drastic drop in speed.

the-evaluator · 3 Dec 2021 at 14:23

There's at least 2 ethernet cables in use, you said that one of them is a known good cable but what about the other?

Check the link speeds that the various bits of kit are showing I expect there's a 100Mbps link somewhere, possibly down to a crap cable.

spenncerr · 3 Dec 2021 at 14:26

the-evaluator said:
There's at least 2 ethernet cables in use, you said that one of them is a known good cable but what about the other?

Check the link speeds that the various bits of kit are showing I expect there's a 100Mbps link somewhere, possibly down to a crap cable.

Wow, I hadn't even thought of that. Surely the cable that came with the deco units is gigabit if the ports are gigabit? I'll check now and let you know!

spenncerr · 3 Dec 2021 at 14:45

I feel pretty stupid for not having checked that sooner.

Turns out my partner had taken out the cat6 from the back of the P9 and replaced it with some shoddy cat5 because she needed a longer wire for her Sonos in her office.

Replaced it now and getting 8x the speed. Thanks @the-evaluator

the-evaluator · 3 Dec 2021 at 14:59

Awesome, good to hear it's sorted.