> # One-Time Password Support

> A one-time password (OTP) is a password that is valid for a single login session or transaction. OTPs avoid a number of shortcomings that are associated with usual (static) passwords. The most vital shortcoming that is addressed by OTPs is that, in contrast to static passwords, they are not at risk to replay attacks. If an intruder manages to record an OTP that was already used to log into a service or to conduct an operation, it will not be misused because it is no longer valid.

> One-time password applies only to RADIUS and TACACS protocol daemons. In the case of the RADIUS protocol daemon, there is no configuration required from the switch side. In the case of the TACACS protocol, ASCII authentication mode needs to be enabled.

> Copyright 2010-2015, Cisco Systems, Inc. All rights reserved.