Anybody with Ethernet knowledge?

[Behemot]

I got this Netgear NAS which does not seem to be working well with GbE. When you plug in the cable it usually tries to connect using GbE (1 to 5 times), than either fails completelly or switches to FastEthernet. Sometimes it works on GbE, sometimes it does not connect at all.

I've started with grounding the RJ-45 metal casing on the PCB as there was some 5 V induced at 50 Hz on the twisted pairs. That came down to 0,5-1 V but still no change in behaviour.

So what may be wrong, the magnetics module or Marvell 88E1116R ethernet controller?

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

Have you tried setting speed and duplex manually on both ends? I don't know that the induced 5v @50Hz would cause a problem since twisted pair is a balanced line, but you might try relocating the wire anyway.

[Behemot]

Re: Anybody with Ethernet knowledge?

I am testing it on unmanaged switch which is laying on a scanner on my PC case, it is not really laying NEXT to AC cable(s), the closes one is at least 10 cm away (cable in the PC PSU), it was just catching it from air.

As the switch is unmanaged and the NAS also does not offer anything related to speed and duplexing in the settings, this is unfortunatelly no go.

[eccerr0r]

Re: Anybody with Ethernet knowledge?

Have you checked with a different cable? I've seen some bad cable that are intermittent or not work, need all four pairs to be connected. Fast Ethernet only needs the base two pairs connected.

I would think that 50Hz/60Hz line noise would be filtered/differential-balanced out for the most part due to the twists and the physical interface...

[Behemot]

Re: Anybody with Ethernet knowledge?

The noise gets filtered with the LinkCom LAN3219 module. As for cable, several cables were supposedly tested by the owner, don't think this is the problem. Cable I use works fine with my PC with GbE.

[stj]

Re: Anybody with Ethernet knowledge?

how are the caps in the nas?

[Behemot]

Re: Anybody with Ethernet knowledge?

They are some most GP surface-mount, measured OK for their types I think. Ripple at +12 V is very low (without discs though, just the PCB on) at some 5 mV.

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

Have you checked with a different cable? I've seen some bad cable that are intermittent or not work, need all four pairs to be connected. Fast Ethernet only needs the base two pairs connected.

I'm sorry but that statement doesn't make sense, two pairs equals four wires.

Full duplex in ethernet always requires four wires (two pairs), regardless of the speed.

[Behemot]

Re: Anybody with Ethernet knowledge?

Nope, Fast Ethernet only requires two pairs and can run on telephone cable or even USB cable.

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

What is a "pair" of anything? Two. 2x2=4. Two pairs of wires equals four wires. Full duplex ethernet over copper requires two pairs of wires, and that's four wires.

[Behemot]

Re: Anybody with Ethernet knowledge?

Correct. But you said "Full duplex in ethernet always requires four wires (two pairs), regardless of the speed." That's wrong.

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

No it isn't wrong. Look it up for yourself.

You ask for advice from someone who knows about something and get it from someone who knows it and then argue with them? What purpose does that serve? Are you asking to learn and get questiones answered or to argue?

[Behemot]

Re: Anybody with Ethernet knowledge?

No, you you look it up. Fast Ethernet (metalic) uses 4 wires, no more, no less, in either half or full duplex. I have personally used that over the USB cable for some time so I guess I know something about that.

Point about bad cable is noted but as I am no idiot, this has already been checked and is not the problem. My guess is the controller itself is bad, as it is not worth replacing (probably could not even obtain it) I can close this.

[stj]

Re: Anybody with Ethernet knowledge?

point is, gigabit uses all pins on the connector.
so if you tried other cables - check the socket & soldering on the socket & transformer maybe.

[Per Hansson]

Re: Anybody with Ethernet knowledge?

Do you know if it ever did work?
Reason I ask is for example on some dreamboxes they put wrong tantalum caps from the factory, so you always have high packetloss...
And in for example ZyXel modems I've seen the caps go bad, switch then worked fine at 10Mbps but lots of packetloss & lost link even at 100Mbps

[Behemot]

Re: Anybody with Ethernet knowledge?

I may have found the problem. According to datasheet, the LAN3219 should be composed of 4 groups of transformers with two windings and central pin, each group. On the primary (cable side), 3 pins are connected all right at each group. But the secondary (IC side), diode tester beeps all of them are connected together.

I can try to remove it to discover whether the module itself is bad or else it is shorted in the Marvell IC.

Per Hansson: I have been told the problem was there from the very beginning but it got worse over time to the extent it almsot does not work at all. Supposedly it sooner or later catches on GbE if the owner messes with the cable/connector, which would indicate bad contact, but I found one position where there is no contact at all and it is OK in the rest. So possibly he only plugs/unplugs it until it starts to work.

As soon as the GbE catches all right, I have 0 packet loss from 100 ping packets.

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

No, you you look it up. Fast Ethernet (metalic) uses 4 wires, no more, no less, in either half or full duplex. I have personally used that over the USB cable for some time so I guess I know something about that.

Point about bad cable is noted but as I am no idiot, this has already been checked and is not the problem. My guess is the controller itself is bad, as it is not worth replacing (probably could not even obtain it) I can close this.

Now what did I say in the first place? Four wires. At first you argued that it doesn't need 4 wires, only two pairs. WTF is the difference? I don't think you're an idiot but you need to read more carefully and not be so ready to argue my friend.

I did not address using phone lines nor USB cables because it is irrelevant, it still requires four conductors. Phone wires are four wires (although only two are needed for POT), and USB cables are four wires with a shield.

http://en.wikipedia.org/wiki/Fast_Ethernet#Copper

[Behemot]

Re: Anybody with Ethernet knowledge?

eccerr0r: FE only uses 4 wires, GbE uses 8
SteveNielsen: no Ethernet always only uses 4
Behemot: FE only uses 4

etc.

The point is, you are wrong so what's this all about? 10BASE-T uses 2 wires, 100BASE-T uses 4 wires, 1000BASE-T uses 8 wires.

[SteveNielsen]

Re: Anybody with Ethernet knowledge?

I'm sorry but that statement doesn't make sense, two pairs equals four wires.

Full duplex in ethernet always requires four wires (two pairs), regardless of the speed.

Get your quoting straight buddy and re-read what was written. I did NOT say "SteveNielsen: no Ethernet always only uses 4". I said full duplex ethernet DOES require 4 wires and that is the truth.

Quoted from previously cited source:
"Full-duplex Ethernet connections work by making simultaneous use of two physical pairs of twisted cable (which are inside the jacket), where one pair is used for receiving packets and one pair is used for sending packets (two pairs per direction for some types of Ethernet), to a directly connected device."

[Behemot]

Re: Anybody with Ethernet knowledge?

You are only talking about 10BASE-T or Fast Ethernet. GbE does not use 2 pairs+2 pairs, it uses all 4 pairs in wholy diferent manner.

Wiki:

In a departure from both 10BASE-T and 100BASE-TX, 1000BASE-T uses all four cable pairs for simultaneous transmission in both directions through the use of adaptive equalization and a five-level pulse amplitude modulation (PAM-5) technique. The symbol rate is identical to that of 100BASE-TX (125 Mbaud) and the noise immunity of the five-level signaling is also identical to that of the three-level signaling in 100BASE-TX, since 1000BASE-T uses four-dimensional trellis coded modulation (TCM) to achieve a 6 dB coding gain across the four pairs.

So no, GbE - which is also full duplex Ethernet - and it is full duplex only does not use 2 pairs each way. It either uses 4 pairs or does not work at all.

Not to mention 10GBASE-T which also only uses 4 pairs or does not work, while it uses 16levels PAM-16.