Massive DNS Requests caused by IPv6

When I do a tcpdump, I notice the issues…..

11:25:27.106997 IP hpc-mn1.52900 > xxx.domain: 28690+ AAAA? bmc72. (23)
11:25:27.107385 IP xxx.domain > hpc-mn1.52900: 28690 NXDomain 0/1/0 (98)
11:25:27.108387 IP hpc-mn1.47867 > xxx.domain: 19474+ AAAA? bmc72. (23)
11:25:27.108933 IP xxx.domain > hpc-mn1.47867: 19474 NXDomain 0/1/0 (98)

AAAA? are IPv6 DNS Request.

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