Error on capture session limit reached

Products

• VMware NSX

Issue/Introduction

• API calls are used to capture packets at Transport node interfaces.
• API calls being used are based on Create an new packet capture session from API documentation NSX-T Data Center REST API
• If more than 2 simultaneous packet captures are run for a single transport node, or more than 4 simultaneous sessions overall, then a "Max capture session limit reached" error is received.
• Sample API call (example shown with curl API calls): 
  
  root@NSX:/tmp# ls |grep body
body_vnic1.json

root@NSX:/tmp# cat body_vnic1.json
{
   "node": "7702fbc6-####-####-####-###########",
   "cappoint": "LOGICALPORT",
   "capvalue": "16288384-####-####-####-##############",
   "capmode": "STANDALONE",
   "direction": "INPUT",
   "capsource": "CLI",
   "options": {
              "values":[
                {"name":"IPPROTO", "value":"0x01"}
               ]
             }
    }
}


root@NSX:/tmp# curl -k -X POST -H "Content-Type: application/json" -u #####:'###########' -d@/tmp/body_vnic1.json 'https://127.0.0.1/api/v1/pktcap/session'
  
  
  
• Sample response when the API call works fine:

{
  "request" : {
    "node" : "7702fbc6-0557-####-####-#################",
    "capsource" : "UI",
    "cappoint" : "LOGICALPORT",
    "capmode" : "STANDALONE",
    "direction" : "INPUT",
    "capvalue" : "0bbb6d9e-003d-####-####-###########",
    "capamount" : 20000,
    "capduration" : 600,
    "options" : {
      "values" : [ {
        "name" : "ipproto",
        "value" : "0x01"
      } ]
    }
  },
  "sessionid" : "f1838874-e5fc-####-####-#############",
  "sessionname" : "f1838874-e5fc-####-####-##############",
  "sessionstatus" : "CREATED",
  "starttime" : 1729202868329,
  "_protection" : "NOT_PROTECTED"
}
  
  
  
• Sample output when the response shows error on session limit reached:
  
  {
  "httpStatus" : "BAD_REQUEST",
  "error_code" : 31005,
  "module_name" : "Packet Capture",
  "error_message" : "Max per host capture session limit reached, limit is : 2"
}
  
  
  Or,
  
  
  {\n  "httpStatus" : "BAD_REQUEST",\n  "error_code" : 31004,\n  "module_name" : "Packet Capture",\n  "error_message" : "Max global capture session limit reached, limit is : 4"\n}'
{
  "httpStatus" : "BAD_REQUEST",
  "error_code" : 31004,
  "module_name" : "Packet Capture",
  "error_message" : "Max global capture session limit reached, limit is : 4"
  
  
  
  
• 2 kinds of limitations can be seen: capture session limit per host, and a global capture session limit.

Environment

VMware NSX

VMware NSX-T 3.x

VMware NSX 4.x

Cause

This is by design. This limit is hard-coded in the product.

Resolution

An enhancement of higher limit will be included in VCF 9.2 . At VCF 9.2 the capture session limit will be at least 6 per host, and at least 50 globally. 

Workaround:

• For the API calls, there is no workaround to break this limit.
• There are many other ways to capture packets. For example , using pktcap commands on ESXi shell.