Equipmet to trace Ethernet signal

[gsan33]

I have Avaya 9641G IP Phone wich reports "No Ethernet" on the screen during initial start. I have intention to trace an Ehternet signal from the very input RJ45 jack throuth the phone mptherboard to the Broadcom communication CPU input pin.
Need youe advice how to: first I have suggested to buy an oscilscope, but not sure what to select, the pro version may become too expencive, and basic version may not capture high frequesncy signal. I really don't what to spend a fortune just for the pleasure to see the Ethernet frames. I also considered to measure just an AC voltage at the Ethernet cable pair... but with lack of experience I finaaly decided to ask experts. So, what would you suggest to visualize and track Ethernet phisical signal flow over the phone mother board?

[stj]

Re: Equipmet to trace Ethernet signal

how does it even know?
is it trying to connect to something?

[gsan33]

Re: Equipmet to trace Ethernet signal

The phone has imbeded startup procedure. When you plug the Ethernet/PoE cable to the phone jack it starts to boot and writes some messages on the screen. After several minuties the phone writes: "No Ehternet" wich sipmply means the phone does not get any Ethernet frame from cable. Surely I have checked all possible connection issues. I finaly disassemebled the phone and looked inside - all electrical contacts seems to be fine, there are connections from input RJ45 pins to the motherboard. First they go to input transformers 1000 BASE –T MAGNETICS MODULES like 24HSS1041A-2 and it suppous to reach out to Broadcom IC. So, I need some equipmet to trace Ethernet pulses coming from a very input right to the Network Processor

[stj]

Re: Equipmet to trace Ethernet signal

what i mean is, there will be no ethernet frame unless it requests something,
and to do that it has to use an address - if your network has a firewall it could block the fone

[CapLeaker]

Re: Equipmet to trace Ethernet signal

Also make sure the phone wasn’t paired to a wifi dongle. If you pair a VOIP phone to a dongle and then disconnected the dongle without unpairing and plug it into an RJ45 cable it will also complain about no Ethernet. Guess how I found out.

Most VOIP phones are POE capable so you don’t get T1000. T100 is all she wrote then, because 2 pairs are used for POE, then you have one pair TX and another pair for RX. Ethernet cable has 4 cable pairs. That’s it. I’d check the VOIP phone if it can handle POE and I would try to power the VOIP phone up that way. Look hard at the Ethernet jack, maybe it’s just a cold solder joint.
If the problem is indeed the jack, it’s going to be hard to find a proper replacement without any schematic or parts diagram. In this case I would look up the data sheet for the responsible IC and see if there is an example circuit. It hopefully will show what magnetics the jack needs.

[gsan33]

Re: Equipmet to trace Ethernet signal

what i mean is, there will be no ethernet frame unless it requests something,
and to do that it has to use an address - if your network has a firewall it could block the fone

Here is what I do to force the Ethernet IC to start transmitting: I disable and enable Ethernet adapter in "Change adapter option" window. As soon as I hit the button "Enable" I immediately see some very low AC voltage right at the transmit pair. After some time, the voltage disappears and then comes back, it is about 0.2-.4 v measured by standard multimeter. I suppose I see a broadcast Ethernet frame, something like ARP request. So, it is really possible to get some transmission in the cable even without an IP address assigned. But using this multimeter is very ugly method to trace Ethernet pulses, so I am looking for some good oscilloscope

[gsan33]

Re: Equipmet to trace Ethernet signal

Also make sure the phone wasn't paired to a wifi dongle. If you pair a VOIP phone to a dongle and then disconnected the dongle without unpairing and plug it into an RJ45 cable it will also complain about no Ethernet. Guess how I found out.

Most VOIP phones are POE capable so you don't get T1000. T100 is all she wrote then, because 2 pairs are used for POE, then you have one pair TX and another pair for RX. Ethernet cable has 4 cable pairs. That's it. I'd check the VOIP phone if it can handle POE and I would try to power the VOIP phone up that way. Look hard at the Ethernet jack, maybe it's just a cold solder joint.
If the problem is indeed the jack, it's going to be hard to find a proper replacement without any schematic or parts diagram. In this case I would look up the data sheet for the responsible IC and see if there is an example circuit. It hopefully will show what magnetics the jack needs.

The phone is pretty old and there is no WI-Fi option. I also worked hard with the input Ethernet jack, I am sure the cable connectivity is OK. I would like to trace Ehternet frames further, over the motherboard. I need to be sure that those frames really reach to the IC pins.

[stj]

Re: Equipmet to trace Ethernet signal

how do you set the i.p. address?
and does the router detect it?

[CapLeaker]

Re: Equipmet to trace Ethernet signal

Maybe it’s set to a different weird IP and subnet?

[gsan33]

Re: Equipmet to trace Ethernet signal

how do you set the i.p. address?
and does the router detect it?

There is no IP address yet, no routers or firewalls. My home PC Ethernet adapter cable goes to PoE injector and goes to the phone. PoE comes via 7-8 and 4-5 pair, it works fine, -48 V comes to phone's motherboard, the phone display and buttons LED are working.

[gsan33]

Re: Equipmet to trace Ethernet signal

Maybe it's set to a different weird IP and subnet?

Could be, but there is nothing like V-Lan or subnets around as there is no yet IP layer, the phone cryout "No Ehternet" it means

1) Connection problems - Jack, Cable, bended pins
2) Receiving tranfomators on the motherboard are out of order, some capasitors are in short ciurcuit, or metal path is destroyed... as result Ehternet electrics do not reach to IC pin

So need advice how to visualize Ehternet pulses, how to trace its track over motherboard

[stj]

Re: Equipmet to trace Ethernet signal

i'm pretty sure you need a router to act as a gateway and DHCP server for either the phone OR windows to actually activate networking.
i know windows wont assign an i.p. to itself if it cant detect a network.

[Alphacentauri]

Re: Equipmet to trace Ethernet signal

Hello,

The phone will probably look for an IP address via DHCP (unless you set a static address) and may just be failing to get an address from the server.

You could try using wireshark or tcpdump to see if anything is been sent on the wire when the phone starts.

[CapLeaker]

Re: Equipmet to trace Ethernet signal

For Avaya stuff look at www.pbxbook.com. There is some useful information there. Also www.voipdocs.io is a good source.

[pedrolane]

Re: Equipmet to trace Ethernet signal

Do yourself a favour and first make a cross test.

If you plug a PC instead of the phone, does it see Ethernet up ?
If you plug the phone on another switch, another port, with another cable, does it still say "no ethernet"

Don't spend time checking router / firewall (layer 3), Ethernet is layer 2, it can work without router. If the Ethernet interface does not come up, it is an Ethernet issue.

As Capleader mentioned, Ethernet 100BT needs 1,2,3,6 pins only to work (2 pairs).
So you can use a cable with only 2 pairs to avoid the phone / the switch to try gigabit.
Also be sure to power the phone with an AC adapter first to test without power-over-ethernet (POE)

If you re sure POE is fine, check on switch side for warning message.
If only RX pair is okay, the switch may see the phone up, but brings the port down after few seconds when autonegotiation failed. if that is the case you can try to disable autoneg on switch side, and force 100 full-duplex.