How NSX Duplicate address detection works and logs to validate

Products

• VMware NSX

Issue/Introduction

Article to describe how the NSX Duplicate address detection works and the respective logs to validate

• Duplicate address detection checks whether a newly discovered IP address is already present on the realized binding list for a different port.
• This check is performed for ports on the same segment. 
• If a duplicate address is detected, the newly discovered address is added to the discovered list, but is not added to the realized binding list. 
• All duplicate IPs have an associated discovery timestamp. If the IP that is on the realized binding list is removed, either by adding it to the ignore binding list or by disabling snooping, the duplicate IP with the oldest timestamp is moved to the realized binding list.
  
  Logs path - NSX Manager - /var/log/syslog
  

  2025-05-09T00:55:37.692Z nsx-mngr.local NSX 1567 - [nsx@6876 comp="nsx-controller" level="INFO" subcomp="ip-discovery"] getAllDuplicatedIpMap: hash Key 000000000000000000000000000000000000000000000000000000000000000000000000000000001111####1111####01011####0100####0010####001010 found key 000000000000000000000000000000000000000000000000000000000000000000000000000000001111####1111####01011####0100####0010####001010 with  entryMsg ip_address {#012  ip_address {#012    ipv4: 288####298#012  }#012  prefix_length: 32#012}#012mac_address {#012  mac: 345####14861#012}#012type: ADDRESS_BINDING_TYPE_VM_TOOLS#012binding_time: 1746752077227#012 on lspId ff8d5c8a-####-4a22-####-7c87####0180 lspId e26414e6-####-4041-####-ac5c####e38c

  
  IPv4 & MAC = Decimal Format

  binding_time = 1746752077227 [Timestamp of the same IP assigned to another machine]

  Existing machine logical switch port = ff8d5c8a-####-4a22-####-7c87####0180

  New machine [which got the same IP] logical switch port = e26414e6-####-4041-####-ac5c####e38c

• Note: If the environment has an APIPA IP as a duplicate, the APIPA IP decimal value always starts from 285 (Example:- ipv4: 2852038914). Based on that, monitoring exclusion has to be configured. 

Environment

VMware NSX
VMware NSX-T Data Center

Resolution

Article to describe how the NSX Duplicate address detection works and the respective logs to validate.