networking – No Bandwidth on long custom lan cable or no connection at all

i have two CAT7 SFTP cable (around 40m long) and two problems. First Cable (12):

1gbps switch --> cat8.1 patch cable --> cat6A keystone jack --> ~40m cat7 SFTP cable --> cat6A keystone jack --> cat8.2 patch cable --> wifi6 AP

Switch says: cable is OK – Estimated cable length is 27.00 – 51.00 m

100mbps HDX  --> ~80 mbps down / ~90 mbps up / ping ~7ms
100mbps FDX  --> ~20 mbps down / ~20 mbps up / ping ~10ms   (connected, a lot of drops and errors like 1000 errors per min on 80mbps)
1gbps   FDX  --> ~ 0 mbps down / ~0  mbps up / ping ~9999ms (no connection, no drops, no errors)

I checked the cable today with a HT Quicklan 6055 and connections a OK.

Two days ago i had an old POE+ AP running on 1gbps (3W, no drops, no errors) on this connection / cable. I changed it to the new wifi6 AP first with POE+ ~7W and it didn’t want to connect with 1gbps. I changed back to the old AP and it didn’t work on 1gbps since then.

I will change the cable to Cat 8.1 SFTP and the keystone jacks to cat8 ones. I wired the cable every time
according to 568 A.

Its a duplex cable, the other one is connected with my computer (same connector types) and it works with 1gbps. The AP connected directly to the switch with one short Cat7 cable delivers 350mbps with no problem.

Could it be an twisted pair wiring problem?
And is there a difference in bandwidth between POE+ (on / off) on this cable length?
Is it recommended to keep POE+ off and use a power adapter where possible?

I am grateful for any ideas!

For my second cable (13):

Same setup as mentioned above, except for the end. There is a adaptor like this one. I checked the cable with the HT Quicklan 6055 and the cable is OK. But switch says:

cable is not OK
Failure is located approximately 7.00 - 28.00 m from the switch.
        Pair A          Pair B          Pair C          Pair D
Length  7.00 - 27.00 m  8.00 - 28.00 m  7.00 - 27.00 m  8.00 - 28.00 m
State   ✗               ✗               ✗               ✗

Same wire was running with passiv poe for two years. Changed to new AP with 1gbps POE+, a new connector (as linked) at the end of Cat7 SFTP and the leds on the switch remains off.

What could be the reason that the cable are connected properly but the switch sees an error on every cable?

ios – iPhone – error copying file or folder – lightning USB-C cable to Windows 10 PC

When I try copying a file from the phone to a computer I get an error “Error Copying File or Folder” – “A device attached to the system is not functioning”

This is running iOS 14.4.2 and the PC is Windows 10. I’ve tried two genuine Apple cables – a USB-C to lightning one and a USB-A to lightning and get the same result.

Rebooting the phone fixes this and I can copy one video and then I start getting the error again.

I’m thankful I at least have a workaround with rebooting, but any thoughts on how to solve so it can work as expected.

Here’s a screenshot of the error:

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If I try again after getting this error I get one saying “The device is unreachable” – see screenshot below:

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What are the risks to my router when behind cable modem?

Many tech sites suggest using dd-wrt as many manufactures have swiss-cheese security with their routers.e.g. Firmware hardcoded “backdoors/admin tools”.

However, if the router is behind a cable modem, do realistic threats exist? Wouldn’t the cable modem be the main target?

Is flashing dd-wrt on one of the better manufactures worth the time and work involved?

root access – Can I use apps like LADB WiFi ADB or Wi-Fi Debugging without needing a USB cable ever during the process?

I have an old Android tablet that had been rooted but my phone hasn’t been rooted….yet.
What I need to understand is if there’s a way to use my tablet to perform edits on my phone without EVER needing a USB cable to do so.
LADB requires Android 11 it seems but my phone (Moto E 2020) isn’t eligible for any system upgrades and as I mentioned above, the phone isn’t rooted. I’ve already downloaded apks like TWRP, LADB, Wireless Debugging and I’ve already enabled adb in the dev options.
So is it possible to connect to the phone using the tablet?

zoom – Goodnotes + Airplay with cable?

A few weeks ago I was trying to give a lecture on Zoom by sharing my iPad screen using Airplay. My Zoom session was through a Mac computer so the connection to the iPad was over the WiFi. The issue I had was things were very laggy. An audience member asked if I was connecting the two devices over WiFi and suggested that was the problem; I should use a cable to connect them.

I’m working on preparing for future lectures and I noticed that the presentation mode in Goodnotes does not work as intended if you go to Zoom, share screen, and “iPhone/iPad via cable.”

When I go to the Goodnotes website, they suggest the following:

1. Connect your iPad to your computer via USB-C or Lightning cable
2. Start or join a Zoom meeting on your computer and click “Share Screen”
3. Select “iPad/iPhone via AirPlay”

I am playing around with my iPad and computer and it seems like, indeed, if the two are connected by a cable, the AirPlay connection will work even if the WiFi on my iPad is off. That just seems counterintuitive to me: you don’t choose the “iPad via cable” option, but instead choose Airplay even though they’re connected with a cable? I also haven’t seen anything online about Airplay working with a hard connection in the event the WiFi is off.

Am I understanding this right? I guess this is more than a solved problem by now. Was the audience member right that for Zoom lectures over Goodnotes, it’s best to use a hard connection (with Airplay)?

external sd – If I plug a 1TB ssd drive to android phone via otg cable, will andorid system scan all media files in the drive?

I concern about performance a lot. Thus I have this question. If I plug a 1TB ssd drive to android phone via otg cable, will andorid system scan all media files in the drive automatically once it gets mounted? Will this cause any performance issue and add more CPU/RAM overhead? If it does it, how to stop this behavior? I just want the system scan the media files when I open a particular folder which contains the media files. I don’t really want the system to scan everything before I actually want to access them. Thanks a lot.

usb on the go – I have connected an OTG cable to my OnePlus device, but nothing happens. What to do?

OnePlus’ OxygenOS (the Android OS that came with your OnePlus device or got updated some time ago) keeps OTG setting disabled by-default. A user has to enable that setting before using their OTG device. The setting can be found in Settings app → System → OTG storage.

If you cannot find that setting there, search for “OTG” term in Settings app and the relevant setting should show up. Once enabled, plug in your OTG cable/adapter along with your accessory and it should work (provided Android supports it of course!)

Do note that the OTG storage setting would auto-disable after 10 minutes of OTG inactivity. So you would have to enable the setting again should you find yourself in need of using your OTG accessory.

To keep the setting enabled all the time, see my answer here (required a rooted OxygenOS).

networking – Separate connections over 1 network cable

Consider the following network setup

┌────────────┐           │               │               ┌───────────────┐
│            │           │  2 Port RJ45  │               │               │
│ ISP / DHCP │──────────▶│  Socket Roof  │──────────────▶│ Unifi AP Roof │
│            │           │               │        B      │               │
└────────────┘     A     └───────────────┘               └───────────────┘
                                │  ▲                                      
                                │  │ B                                    
                                │  │                                      
                                │  │                                      
                             CAT6 Split                                   
                                │  │                                      
                                │  │                                      
                              A │  │                                      
                                │  │                                      
                                ▼  │                                      
                         │  2 Port RJ45  │                                
                         │ Socket Ground │     B                          
                      ┌──│     Floor     │◀───────────────────────┐       
                      │  │               │                        │       
                      │  └───────────────┘                        │       
                      │                                           │       
                      │                                           │       
                   A  │                                           │       
                      │                                           │       
                      │      ┌────────┐               ┌────────┐  │       
                      │      │ Unifi  │        B      │ Unifi  │  │       
                      └─────▶│  USG   │──────────────▶│  PoE   │──┘       
                       WAN/1 │        │ LAN/1         │ Switch │          
                             └────────┘               └────────┘                  

Now the issue is there is only one cable run from the roof to the network rack on the ground floor. To get 2 connections out of this I have split the CAT6 cable up into 2×100 MBit using 4 wires each.

So the network is as follows:

  • The ISP comes in on the roof via a standard RJ45 (radio relay)
  • The cable is then connected to a 2 port socket (port A) I wired up to split the cable into
  • On the ground floor the cable from A is connected to the USGs WAN/1 port.
  • From the USG LAN/1 port it goes to a PoE switch that connects the rest of the local lan
  • One PoE port from that switch goes back to the 2 Port socket on port B
  • Port B of the socket on the roof is then connected to the AP

Now I can’t say I really like this setup very much. The reasons this is set up this way is

  1. I am a network noob and probably don’t know better
  2. I wanted to power the roof AP via POE without an additional injector (not that important)
  3. I wanted to isolate the ISPs DHCP by splitting it into 2 physical connections and using the USGs DHCP instead (important)

So the question is:

Can I achieve those goals without splitting the cable up into 2x100MBit, e.g. using a USW Flex Mini switch?