Usually MAC address is 48bit - 6 pairs of characters, e.g. 00:18:18:d1:f0:7c However some fiber switch interfaces may have 'long' MAC addresses, which is 64bit MAC address e.g. 00:18:18:d1:f0:7c:8a:5b
The 64bit MAC address seems to be EUI-64 standard:
When pattern discovers these MAC addresses and save, they will be truncated to the maximum length of the MAC address field which is 18 characters. For example "22:ad:00:0d:ec:25:e8:40" will be truncated to "22:ad:00:0d:ec:25:". Then next time Discovery compares the MAC address "22:ad:00:0d:ec:25:e8:40" and "22:ad:00:0d:ec:25:" and decides to create a new CI because no match can be found. This will create duplicated Network adapters for every Discovery run.
Steps to Reproduce
Discovery a server/device which uses EUI-64 standard 64bit MAC address
The workaround is to increase the maximum length of MAC address field on cmdb_ci_network_adapter to 24, so the EUI-64 MAC address would not be truncated.
Related Problem: PRB1411504