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YiWang
Posts: 12
Registered: ‎10-01-2012

Hub -- Model No. EFAH05W

Hi guys,

 

I bought an EtherFast 10/100 workgroup hub (Model No. EFAH05W) and I got a problem here.

 

I think hub is a network repeater, so if I send one packet from PC1 to device (dest addr: 00:00:00:00:00:03, src addr: 00:00:00:00:00:01) through hub, PC2 can also get this packet, right?

 

But the fact is:

 

  1. One packet from PC1 to device (dest addr: 00:00:00:00:00:03, src addr: 00:00:00:00:00:01), only device can get this packet, no PC2.
  2. One broadcast packet from PC1 to network (dest addr: FF:FF:FF:FF:FF:FF, src addr: 00:00:00:00:00:01), PC2 and device can get this packet.
  3. One packet from PC1 to an invalid target (dest addr: 00:24:54:00:00:06 (invalid mac address), src addr: 00:00:00:00:00:01), PC2 and device can get this packet.

 hub.png

 

 

 

 

 

 

 

 

 

 

Can you tell me if those situations are correct? Your hub can filter mac address as switch??

 

Thanks in advance!

 

Jake_2.0
Posts: 2,157
Registered: ‎05-29-2012

Re: Hub -- Model No. EFAH05W

This is just a normal hub or just a pass through device. If you want the computers to communicate to one another then try to assign a static ip address on each computer and try to ping them. You might need to disable the computer's firewall for them to communicate with one another.

YiWang
Posts: 12
Registered: ‎10-01-2012

Re: Hub -- Model No. EFAH05W

Sorry, I don't get it. My packet doesn't use ip protocol but my own protocol on data link layer which means mac address is uniquely identity to communicate.

 

I want every hub port can get the all packets from other ports, is it possible on data link layer?

 

Thank you very much!!

YiWang
Posts: 12
Registered: ‎10-01-2012

Re: Hub -- Model No. EFAH05W

let me make thing clear here.

 

if Device sends a packet to PC1(dest Mac addr: 00:00:00:00:00:01, src Mac addr: 00:00:00:00:00:03 ) through hub, why PC2 couldn't get the packet, only PC1??

 

if Device sends a broadcast packet or invalid dest Mac addr, all PCs can get this packet.

 

I think it's not related to firewall because PCs still can get the packet from device.

 

Thanks!!

 

Expert
zee29
Posts: 1,329
Registered: ‎04-22-2012

Re: Hub -- Model No. EFAH05W

Hmmm hubs are known to be dumb devices. So all devices connected to it will be able to communicate with each other. Why not remove PC1 then test the connection just to see if the PC2 will be able to receive that packet.

YiWang
Posts: 12
Registered: ‎10-01-2012

Re: Hub -- Model No. EFAH05W

Thanks for your reply!  I did some experiments for this.

 

PC1, PC2 and device connect with hub together. Let's say PC1 with port1, PC2 with port2, device with port 4.

 

1) When device sends one packet to PC1 (dest mac addr: 00:00:00:00:00:01, src mac addr: 00:00:00:00:00:03) through hub, PC2 couldn't get this packet.

 

2) When I remove PC1 and device sends the same packet again, PC2 still couldn't get this packet.

 

3) If I change PC2 (port 2) to port1 that previously connected by PC1, device sends the same packet and PC2 can get this packet. (PC1 is still removed.)

 

4) If I change PC2 to other ports which are not port1, PC2 couldn’t get this packet. (PC1 is still removed.)

 

5) I reboot hub (turn off and turn on the power), and test again without PC1. PC2 can get the device packet through all ports.

 

6) Once I connect PC1 to hub again, only that port can get the packet until PC1 changes its port.

 

So I think your hub can detect the mac address of PC1 once PC1 connect with hub and not broadcast the packet belongs to PC1.

 

My purpose of this project is to use PC2 as a network sniffer to get the packets between PC1 and device on the data link layer using winpcap. Do you think it’s possible? 

opheliaimmortal23
Posts: 1,644
Registered: ‎05-04-2012

Re: Hub -- Model No. EFAH05W

Is your hub connected to a modem or a router? I think this setup you want will only be possible if you have a device that is DHCP server.

YiWang
Posts: 12
Registered: ‎10-01-2012

Re: Hub -- Model No. EFAH05W

My hub isn't connected to modem or a router above those experiments. My device is an evaluation board. 

You mean if I try to set up a network sniffer on PC2, I need a DHCP server?

 

Anyway, I connected a router to hub and test again, the same result. I am very confused about why PC2 cannot get the PC1 packet?? It should get this packet, right?

 

Thanks!!!

 

YiWang
Posts: 12
Registered: ‎10-01-2012

Re: Hub -- Model No. EFAH05W

[ Edited ]

Do you guys know how to test this hub as a repeater?

Expert
zee29
Posts: 1,329
Registered: ‎04-22-2012

Re: Hub -- Model No. EFAH05W

I agree it should get the packet since the hub is broadcasting it to all devices. What tool are you using to send the packet? Did you assign any ip address to the computers? The test that you did is actually good, but since we have proven that the port where pc2 is not receiving the packet it could also mean that the port is busted.