When Zabbix agent validates incoming passive-check connections against the configured Server= IP adresses - it appears to resolve configured peers through getaddrinfo() in the allowed peers validation path.
In the affected environment Server= is configured with numeric IP addresses only.
During peer validation agent generates a high number of DNS queries with search domains suffixed to the numeric-looking values. This is unexpected because Zabbix agent seems to use the IP address as a hostname. It seems that the server IPs are used like a shortname of host trying to locate it in the search domain specified.
Querying DNS has been tracked by tcpdump with the command:

tcpdump -i en0 dst <name_server_IP> and port 53 -nn -vv -tttt |nl

Steps to reproduce:

• install Zabbix agent version 6.0.34, 7.0.10, or 7.0.18 on AIX
• configure passive agent mode Server= using numeric IP addresses only
• ensure the OS resolver has at lest one DNS search domain configured
• link the Zabbix default templates for AIX
• start or restart the Zabbix agent
• initiate passive checks from a Zabbix server
• monitor DNS traffic from the agent host

Result:
Zabbix agent host generates many DNS queries while validating incoming connections against Server= IP values
Observed pattern:
<IP_address>.example.domain

Expected:
For IP address entries in Server= - Zabbix agent should not invoke DNS or any other name-resolution service, IP should be handled as numeric address only.