How do I determine the MTU setting on the ports on 3Com Superstack 4400 PWR Switch

We are having issues with a Barracuda Spam Firewall 300 and their support is asking for the MTU setting on the switch. We have connected the Barracuda to two other switches and replaced the Ethernet cable and still have excessive collisions - considering we are seeing none from any other network devices.

The 3Com 4400 would be set to the defaults (whatever they may be), but, I have no way of determining what that is and my discussions with Barracuda Networks are at a standstill until I furnish them the information. The Barracuda device MTU is set to 1500.

Any suggestions or info would be appreciated!
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I looked through the menu system too and see no way to get to that on the 4400.
I suspect the default, and maybe only setting in this switch, is 1500.
display interface command
kdf_algerAuthor Commented:
I found  this a couple days ago, but, I am not knowledgeable enough to know how / where to enter this command. I connected to the switch with Telnet and navigated the available menus. I never found the secret to being able to type this command.
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Sorry that command is for a 4200. In the 4400 menu system I think it would be under physicalinterface or protocol - ip - interface. I don't know if you can do anything else but the menus and the web interface on the 4400s.
kdf_algerAuthor Commented:
I checked the web interface and connected via Telnet, again, and was unable to locate the information. I am not sure where else to look. Perhaps this setting is not configurable in the 4400?

use this command
display interface [ interface_type | interface_type interface_number ]

--- interface_type: this can be either Aux, Ethernet, GigabitEthernet , NULL, Vlan-interface.
--- interface_number: Enter the interface number in the format unit-number/0/port-number.

<switch>display interface Ethernet 1/0/1

Ethernet1/0/1 current state : UP
IP Sending Frames' Format is PKTFMT_ETHNT_2, Hardware address is 00e0-fc00-0010
The Maximum Transmit Unit is 1500  >>> MTU = 1500
Media type is twisted pair, loopback not set
Port hardware type is 100_BASE_TX
100Mbps-speed mode, full-duplex mode
Link speed type is autonegotiation, link duplex type is autonegotiation

kdf_algerAuthor Commented:
As I explained earlier, I am unable to find anything but a menu that gives me options: bridge, feature, gettingStarted, logout, physicalInterface, protocol, security, system, trafficManagement... I have navigated all of the options and have yet to find myself anywhere that tells me the MTU or allows me to configure it. This is basically the same information that I can view by logging in with a GUI, rather than Telnet.

Port:   1:14    State:  enabled      Mode:  100full (Auto)
Media Type: 10BASE-T/100BASE-TX
Active Features : STAP Enabled, BSC Enabled

Refresh Time:10 Seconds

-Counters-                           -Rx-                    -Tx-
Unicast Packets:             2107352                 2001038
Non Unicast Packets:            3293                 3693769
Octets:                        1575408363              2214480750
Fragments(Rx)/Collisions(Tx):         0                       0
Discarded Packets(Rx):                  0                       -

-Rx Errors-
Undersize:                  0           Oversize:                    0
CRC Error:                  0           Jabbers:                      0

-Pkt Analysis-
64 Octets:                1740676           256 to 511 Octets:      227268
65 to 127 Octets:     2410674           512 to 1023 Octets:      66485
128 to 255 Octets:    1347461          1024 to 1518 Octets:   2012888

Quit    Counters      Differences      Rates/Sec     Utilizations

Please excuse my ignorance, BUT, where do I use the command you listed with a 3Com Super Stack 4400?
telnet its IP :: or use its console com port ??
then use that command ..
Can you check with 3Com support and confirm whether this can be done on this model switch?
kdf_algerAuthor Commented:
We called 3Com and they were unwilling to discuss the matter or tell us the default. Perhaps if we connected to the com port, there may be a console where we could enter other commands. At this point, we are going to assume that the MTU is 1500 and cannot be changed. This mission was initiated by Barracuda Networks support, because our SPAM firewall is causing collisions on the 3Com SS 4400 switch. It should be noted, that we observed the same issue on another switch.

Although the number of collisions that we are seeing could be considered meaningless (slightly over 5%), the network adapter in the Barracuda will not negotiate a full duplex connection with any switch we connect it to, even though Barracuda support the adapter to force it to be full duplex.

Thank you all for your input!
Thye only thiong I can suggest, if you haven't already, is set the switch port to FDX as well vs Autonegotiate.
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