This is the rn (Relative Name), the single naming segment that, appended to its parent's dn, forms the full dn for this one instance of one IPv4 address record drawn from a management IP pool, used to auto-assign an out-of-band management IP (typically to a server's CIMC) instead of a static address. UCS Manager derives this segment automatically from the object's own defining attribute (such as an address, index, or configured name), so seeing a distinctive rn like this is how you tell one Addr row apart from every sibling row under the same parent. For this class the rn typically looks like 'addr-10.10.10.23'.