one switch is slower then then the othet.

[LordGarfield]

Ok this is the situation.

Let me describe my infrastructure.
I have a router wich goes to the internet on one side and the other side goes to a 6 port switch.
in this switch there are 3 servers plugged in and 2 parts of a network. One part is the building where my MDF is in. The other part is another building that comes in with fiber optic cable wich is converted to utp.

everything is 100mbit. so the fiber also works like it is a long UTP cable with 100mbit as max traffic.

now the network wich is behind the fiber is smaler then the other one. All pc's there where connected with one HUB and this hub was pluged in to the fiber convertor and so it went to the other building.

Now a program called navision was verry slow on this side of the network. So we tried to find the problem. We also getted a 1 gigabit swith from sombody. One we could borrow for a moment. (its a 3com one) And poof everything was verry fast. great. So what did we do. We bought ourselfes a 3com switch but a 100mbit one becouse everything is 100mbit and if you send 100mbit and recieve against 100 mbit it does not mather that this switch is 1gb or 100mbit.

but gues what. We putted the new swith in and everything was slower again. Much slower. So first thing you think is to test the swith on the other part of the network where there are no problems but wich is bigger. I plugged this swith in so that it replaces another switch their and it gives no difrence. It is fast. It is like fast as the 1gb switch on the network behind the fiber.

So what is the problem here?
both switcher are 3com.

Greetings
Roel.

 

[jimbopalmer]

OK, I want to pretend this is all about duplex, so let me ramble.

Hubs only let one packet be transmitted at once, every port sees the same info, of they want it or not. Since only one port can be talking, it is half duplex.

Switch ports can do half duplex or even better, full duplex where the port is transmitting and recieving at once.

all of the UTP protocols (10baseT, 100baseTX, 1000baseTX,etc) include an option to auto negotiate speed and duplex. if you set them to auto, all is well.( if the wire is less capible than the ports you may need to hand choose speed/duplex, also some vendors seem to do 'auto' poorly, Cisco and Apple come to mind)

Sadly, the fiber protocols do NOT have an auto setting ususally (100baseSX is 'new' but is rare and does auto) I suspect one side is set to full, while the other side is set to half

If one side think it is free to send AND receive and the other side thinks it has to send OR receive, they will spend most of the time disagreeing, not sending user data.

Try setting both sides to half duplex, every device can do that. the hub cannot do full duplex so as long as it is one end of the fiber, you cannot do full duplex.

IF you are replacing the Hub (it is hard to tell) so that you have switches on both sides, then full duplex is faster than half duplex.

(none of this is the fault of 3com, I fight it all the time in Nortel equipment over fiber, Cisco customers even have to fight it in copper)


I tried to remain child-like, all I acheived was childish.

 

[LordGarfield]

Hi tanks for answering. but.

well I was replacing the hub.
With a switch. But I tried 2 switches to replaced the hub. Both gave difrent results. One switch is faster then the other. and they both autonegotiate about speed. And they'r both 3com. (I don't attack 3com it is just informative.)

greets.

 

[jimbopalmer]

But auto-negotiate CAN'T work right over fiber, you HAVE to set the fiber duplex manually. (the speed is fixed) Set it the same at each end of the finber and all will be well.

I tried to remain child-like, all I acheived was childish.

 

[LordGarfield]

This is the switch I have. How can config this switch. There is nothing in the manual?

3COM 3C16471 Euro355,00

Ports: 24 autosensing, auto-configuration MDI/MDIX 10BASE-T/100BASE-TX

Media interfaces: RJ-45

Ethernet switching features: Full-rate nonblocking on all Ethernet ports, full/half duplex auto-negotiation and flow control, 802.1p traffic prioritization
MAC addresses supported: 4,000


tanks

 

[jimbopalmer]

Yes the 3C17300 seems to be the cheapest 3com switch you could control the duplex on. Perhaps we can control it at the converter.

You must be using an external copper to fiber converter with the 3com switches, do you know the vendor and model of them?

http://www.mrv.com/product/MRV-FD-NMSW/

is a fiber to copper converter that allows the copper side to be auto-negotiate like you need.

http://www.ethercom.com/efm14.html

is another model with auto negotiate electronics

http://www.lantechuk.com/products/lan/converter/multi-converter/modular-converter.htm

the option B) model has blinky lights for duplex so you could know what it chose.

I tried to remain child-like, all I acheived was childish.