I never saw this before.
One server has
255.255.255.255:bootps <=> *
when running iftop with data going back and forth.
15:31:29.539882 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from 00:0a:e6:fa:11:9e, length: 300
15:31:29.540756 IP 0.0.0.0.bootpc >...