I have a 3com switch 4210, I have 2 certified conections witch fluke 1200. One conections function good, transmit and receiv packet from a pc, but the other not receiv any packet. I change, patch cord, sitch port, etc. The problem seems to be the cable but it will clear the certification. 3com make some extra testing that does not allow to establish the connection?

Take the Huawei S2700-9TP-SI-AC for example:
After the VLAN translation function is enabled for the Huawei S2700 switch, the 128 module problem exists because the chip difference supports only 128 VLAN TO VLAN entries.
The packets received through the port are processed as the VLAN smaller than 128. The calculation method is (vlanid)%128.
Therefore, for a VLAN greater than 128, port vlan-mapping vlan id map-vlan id, that is, the mapping from the VLAN to the same VLAN, must be configured for the transparent transmission to be implemented.
More related:
Huawei S2700-9TP-EI-AC
Huawei S2700-9TP-EI-DC
Huawei S2700-9TP-PWR-EI

You can enable a switch to transparently transmit BPDUs in the following modes:
1. Run the bpdu bridge enable command to enable the port bridge function. Then the switch can transparently transmit all BPDUs.
2. Globally specify the group MAC address of BPDU for the inbound and outbound ports of two edge switches on the network, and enable the L2PT transparent transmission function of the protocol for the ports.
Incoming BPDUs are replaced with the group MAC address, converted to data packets, and forwarded in the VLAN. Configure the L2PT function in the outbound port to replace the group MAC address with the BPDU MAC address.

Make sure its not blocked from the router settings and the corresponding port is open.

You should be able to chain together. Only change IP scope on second unit to avoid any IP conflicts.

Transmitted Error Count 4734440

Ack Rcv failure Count 15269951

• As per the above there are error on Transmitting the packet and also for receiving the acknowledge packet.
• Please check whether any disturbance in the link
• Each PPP packet has a checksum attached to ensure that the data being received is the data being sent. If the FCS of an incoming packet is incorrect, the packet is dropped and the HDLC FCS count is increased.
• Another reason for seeing too many FCS errors may be that the remote end has stopped talking PPP.

Be sure that when you say its a hub that is indeed a layer 1 device which is just passing the signal and data along to all ports. Be sure to check the cable on the second device. At this point it must a straight cable you use to connect the PCs to the Hub. PCs transmit on pins 1 & 2 and Receive on 3 & 6. Hubs are the opposite. So a crossover will not work. You need PC pin 1 & 2 Tx to Hub Pin 1 & 2 Rx and over to PC pin 3 & 6 Rx to Hub pin 3 and 6 Tx. Tx = transmit and Rx = Receive. Also assign an IP address on each machine that is in the same subnet as each other. Such as PC1 192.168.1.100 mask 255.255.255.0 and PC2 IP address as 192.168.1.101 Subnet Mask 255.255.255.0 This way the 192.168.1 is the same for 8 PCs and the only change is the last number (octet). Also keep the speeds at either 10/100/1000 what ever the product is rated for but always keep the duplex half. Half is good because on a layer 1 hub, everyone is broadcasting at the same time. So you have to have half of all the ports listening at all times.

I hope this helps. My advice is to buy a layer 2 switch.

Test connection, see if you pulled an IP address
Go to the Windows desktop
Select Start then Run
In the text box type: cmd (WIN98/SE type command)
At the command prompt type: ipconfig
4. What does it read as the IP address?
* If it reads 192.168. something dot something then you are pulling
an IP address and are connected to the network. The problem is
software related, check your firewall, and wireless card configuration.
Also check any WPA or WEP encryption keys. Check with the respective
manufactures.
* If it reads 0.0.0.0 for the IP address you are not connected to the network.
* Check your connection configuration and the adaptor.
* Check with the respective manufactures.
STEP TWO/ Basic troubleshooting continued....Testing the adaptor
1. Go to Windows desktop
2. Select Start then Run
3. In the text box type: cmd (WIN98/SE type command)
A DOS window will open.
4. At the prompt type: ping 127.0.0.1 (reserved IP address for all adaptors)
5. Check the line that reads "packets sent = 4, Received = 4, Lost = 0
A. Zero is good, the adaptor is working. Again check the connection
configuration,and the adaptor configuration.
It may be a power issue especially with older or less expensive computers
or wireless cards.
* Check the antenna location, are you inside or outside, look for interference.
* Check with the respective manufactures.
B. If it reads all 4 packets lost, the adaptor is not functioning.
* Check and update the drivers, Contact the respective manufactures.
* If it shows any number of packets lost (you are dropping packets)
it is an adaptor or signal strength issue (generally form the laptop side,
not being able to reach back) especially with older or less expensive
computers or wireless cards.
* Update the drivers
* Check antenna location, or distance from the signal
* Contact the respective manufactures.

switch dont restart by themselves without command, first remove the switch from the network, disconnect from internet, make sure you hadn't fired anybody recently it sounds like a hack. reduce network traffic to local area only and priortise important internet traffic. now got back to the switch and troubleshoot make to check the reboot command on error or when error is found, if the problem stops when the switch is remove somebody is messing with the network.or the darn switch is faulty install a new one.

The 3Com OfficeConnect Cable/DSL Secure Gateway includes all the security features provided by the 3Com OfficeConnect Cable/DSL Gateway, plus a full-function stateful packet inspection firewall for additional security. The 3Com OfficeConnect Cable/DSL Secure Gateway also provides VPN initiation/termination that supports the PPTP, IPSec, L2TP/IPSec, and VPN protocols.