Wasted Bandwidth - Bandwidth is used to transport unnecessary updates. Because RIP updates are either broadcasted or multicasted; therefore, switches also forward the updates out all ports.
Wasted Resources - All devices on the LAN must process the update up to the transport layers, at which point the devices will discard the update.
Security Risk - Advertising updates on a broadcast network is a security risk. RIP updates can be intercepted with packet sniffing software. Routing updates can be modified and sent back to the router, corrupting the routing table with false metrics that misdirect traffic.
Use the passive-interface router configuration command to prevent the transmission of routing updates through a router interface, but still allow that network to be advertised to other routers. The command stops routing updates out the specified interface. However, the network that the specified interface belongs to is still advertised in routing updates that are sent out other interfaces.