RIP Password
String of up to 16 characters. The first character cannot be a question mark (?). The password is sent in the packet as clear text, so no security is provided. The purpose of the authentication is to prevent any RIP packets from being accepted unless the router they come from has been explicitly configured to be part of the routing protocol. This feature can help the administrator protect against misconfiguration but not intruders.
RIP password adds an additional 20 bytes of overhead for every 24 routes sent by RIP-2 because the authentication occupies the first route slot in every RIP-2 packet sent. If authentication is configured, any RIP version 1 (RIP-1) packet and any RIP-2 packet without a matching password are dropped on receipt.