Triaging because I have already seen this weirdness. Subnets aren't intended to overlap. The IP range of one subnet should be unique compared to every other subnet on the same segment. This is mainly because routers can't reliably determine which subnet should get a packet destined for one of the overlapping addresses. That might be what's gumming up the rack controller in this instance, dunno.
That said, I'm not sure if MAAS should prevent you from doing it, that is, I'm not sure if it's a doc/troubleshooting bug or a code bug. Either way, we should talk about it.
Triaging because I have already seen this weirdness. Subnets aren't intended to overlap. The IP range of one subnet should be unique compared to every other subnet on the same segment. This is mainly because routers can't reliably determine which subnet should get a packet destined for one of the overlapping addresses. That might be what's gumming up the rack controller in this instance, dunno.
That said, I'm not sure if MAAS should prevent you from doing it, that is, I'm not sure if it's a doc/troubleshooting bug or a code bug. Either way, we should talk about it.