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EMS Event "netif.tcp.conn.bad.checksum"

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Category:
ontap-9
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nas
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Applies to

  • ONTAP 9.11.1 and later
  • Transmission Control Protocol (TCP)
  • Internet Protocol (IP)
  • Networking 

Issue

  • Multiple netif.tcp.conn.bad.checksum:error events are seen for different source and destination addresses :
[node01: kernel: netif.tcp.conn.bad.checksum:error]: TCP packet with bad checksum detected on port e0c. The packet arrived on connection with source address 10.0.0.10 and destination_address 10.0.0.1
[node01: kernel: netif.tcp.conn.bad.checksum:error]: TCP packet with bad checksum detected on port e0c. The packet arrived on connection with source address 10.0.0.11 and destination_address 10.0.0.1
[node01: kernel: netif.tcp.conn.bad.checksum:error]: TCP packet with bad checksum detected on port e0c. The packet arrived on connection with source address 10.0.0.12 and destination_address 10.0.0.2
[node01: kernel: netif.tcp.conn.bad.checksum:error]: TCP packet with bad checksum detected on port e0c. The packet arrived on connection with source address 10.0.0.10 and destination_address 10.0.0.2
or

<LR d="10Oct2025 04:20:09" n="node-01" t="1760037609" id="1749258895/33018" p="3" s="Ok" o="kernel" vf="" type="0" seq="270937" >
<netif_tcp_conn_bad_checksum_1
local_port="e0f"
source_address="10.63.255.1X"
destination_address="10.63.255.2X"/>

Note: The source address is usually a client address. The destination address is the Network Interface (LIF) address of the node 

  • Bad TCP cksum is also incrementing on the port in the ifstats of the node ::> system node run -node node_name -command ifstat port_name:

-- interface  e0c  (40 days, 5 hours, 34 minutes, 37 seconds) --
RECEIVE
Total frames:     2047m | Frames/second:     589  | Total bytes:      2625g
Bytes/second:      755k | Total errors:        0  | Errors/minute:       0
...
LRO bytes:        2527g | LRO6 segments:       0  | LRO6 bytes:          0
 Bad UDP cksum:       0  | Bad UDP6 cksum:      0  | Bad TCP cksum:      21
 Bad TCP6 cksum:      0  | Mcast v6 solicit:    0  | Lagg errors:         0
...

  • Additional steps checked :
    • Verified if any CRC errors  under ifstat, troubleshoot the cable/SFP connected to the port  if CRC errors are visible
    • If no CRC errors are reported in ifstat:
      • If a single client is being reported in the EMS message, investigate the client
      • Otherwise, if no trend in clients, investigate devices between the client IP's and LIFs mentioned in the EMS message
      • Ensured correct MTU is set on all interfaces (storage, switch, host)

Note: Collect simultaneous tcpdumps or packet traces from impacted port on storage, connected switch port and the client to confirm TCP bad checksums. There is currently no other known method to rule out contributors or determine the cause

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