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Community Member

35xx XL input errors with 3C905C-TX-M

Gives lots of input errors. CRC en frame errors

Settings are both on switch and NIC 100 Mb Full duplex. What about other settings on the 3C905C-TX-M NIC. Such as: 802.1p support, flow control, RX Checksum Offload and Tx Checksum Offload

Community Member

Re: 35xx XL input errors with 3C905C-TX-M


i have same hardware 3548 3com905c, settings fdx,100mbps and same probs. btw running win2k.

see my post. bye

Community Member

Re: 35xx XL input errors with 3C905C-TX-M


In future refer to this link for NIC card issues

The issue you are seeing is a known issue documented in CISCO bug ID and it is a 3com bug.

CSCdt68700 - Switch reports FCS, Alignment, Runts when 3C905C connected at FD

Release notes

Under normal traffic conditions, a 100 Megabit, Full-duplex connection between

any Cisco Catalyst Switch and a 3Com 3C905C will result in Layer 2 errors. The

Catalyst Switch will report these Layer 2 errors as FCS, Alignment and Runt


Troubleshoot this issue by reviewing the below guidelines and documentation.

1. Verify that both the 3Com 3C905C and Catalyst Switch are both set for

auto-negotiate or both are manually set for 100 MB, Full-Duplex. A duplex

mismatch will cause a higher rate of Layer 2 (physical) layer errored frames.

2. Load the lastest 3Com 3C905C driver available from

3. Load the diagnostic utility available with the lastest 3Com 3C905C driver.

update.exe /diag)

4. Connect 2 test workstations with 3Com 3C905Cs back-to-back using a crossover


5. Test Connectivity initiating a large file transfer between the workstations

and noting the following counters with the 3Com Diag Utility. This test, the

back-to-back between the PCs with 3C905C(s), will give a benchmark for performance and physical layer errors.

According to the 3Com documentation, the details of the following counters are


Receive Overruns: Receive Overrun is the number of lost packets that cannot be

stored in the receive buffer because the PC's buffer is already full.

Carrier Sense Lost: Carrier Sense Lost is the number of packets transmitted

with a carrier sense loss. This normally occurs as a result of collisions.

Transmit Underrun: Transmit underrun is the number of times a packets was

transmitted without adequate data by the NIC.

In respective the Catalyst Switch Counters, a packet transferred that results in

the Carrier Sense Lost or Transmit Underrun incrementing on the 3Com NIC will

cause at least one of the following counters to increase on the Switch:

Alignment, FCS, CRC, Input Errors, Receive Errors, and/or Runts.

Noting the errors and performance back-to-back between 2 PCs with the 3C905C

NIC will give a minimum baseline for the number of errors reported by the switch

and a generally baseline for performance.

6. Repeat step 5 with the PCs connected to the switch and baseline the number

of errors to the errors recorded in Step 5. Expect a higher number of errors

when the workstation is connected to the network as there will be higher load of

traffic including multicast, unicast-flood, and broadcast traffic.

Note: It has been noted that increasing CPU/BUS Speed on the workstation

increases the number of Transmit Underrun packets recorded on the NIC and Runt

Packets on the Catalyst Switches.

In conclusion, this issue is not a Switch specific issue nor an issue with

compatability. Please contact 3Com Tech Support for resolution.

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