onesixtyone scans SNMP community strings. Simple Network Management Protocol, after all, does indeed offer management.
From the website:
onesixtyone takes a different approach to SNMP scanning. It takes advantage of the fact that SNMP is a connectionless protocol and sends all SNMP requests as fast as it can. Then the scanner waits for responses to come back and logs them, in a fashion similar to Nmap ping sweeps. By default onesixtyone waits for 10 milliseconds between sending packets, which is adequate for 100Mbs switched networks. The user can adjust this value via the -w command line option. If set to 0, the scanner will send packets as fast as the kernel would accept them, which may lead to packet drop.