For starters you can use the tool ethtool to run your NIC's self tests.
excerpt from man page ethtool -t|--test DEVNAME Execute adapter self test
Example
$ sudo ethtool -t eth0 The test result is PASS The test extra info: Register test (offline) 0 Eeprom test (offline) 0 Interrupt test (offline) 0 Loopback test (offline) 0 Link test (on/offline) 0
Looking at the statistics for the NIC may be useful too in terms of diagnosing your issue further.
$ sudo ethtool -S eth0 NIC statistics: rx_packets: 988097069 tx_packets: 589028032 rx_bytes: 1291674232357 tx_bytes: 116257143322 rx_broadcast: 210375 tx_broadcast: 34690 rx_multicast: 69184 tx_multicast: 179 rx_errors: 0 tx_errors: 0 tx_dropped: 0 multicast: 69184 collisions: 0 rx_length_errors: 0 rx_over_errors: 0 rx_crc_errors: 0 rx_frame_errors: 0 rx_no_buffer_count: 0 rx_missed_errors: 0 tx_aborted_errors: 0 tx_carrier_errors: 0 tx_fifo_errors: 0 tx_heartbeat_errors: 0 tx_window_errors: 0 tx_abort_late_coll: 0 tx_deferred_ok: 0 tx_single_coll_ok: 0 tx_multi_coll_ok: 0 tx_timeout_count: 0 tx_restart_queue: 346104 rx_long_length_errors: 0 rx_short_length_errors: 0 rx_align_errors: 0 tx_tcp_seg_good: 0 tx_tcp_seg_failed: 0 rx_flow_control_xon: 56 rx_flow_control_xoff: 56 tx_flow_control_xon: 0 tx_flow_control_xoff: 0 rx_long_byte_count: 1291674232357 rx_csum_offload_good: 987406053 rx_csum_offload_errors: 3730 rx_header_split: 0 alloc_rx_buff_failed: 0 tx_smbus: 0 rx_smbus: 0 dropped_smbus: 0 rx_dma_failed: 0 tx_dma_failed: 0
Any of the statistics that have the string "error" in them should be zero. If they aren't then I would pursue what may have caused these.
