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 a contiguous IPv4 address range (block) defined within a management IP pool, the from/to boundaries UCS Manager draws individual addresses from. 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 Block row apart from every sibling row under the same parent. For this class the rn typically looks like 'block-10.10.10.10-10.10.10.50'.