switches could drop Rogue Router Advertisements (e.g. based on the direction from where a Router Advertisement arrived at a switch - this is called Router Advertisement Guard (RA-Guard in RFC 6105), or routers could be running 'prefix depreciation tools' that would detect when Rogue Router Advertisement messages were sent to hosts and then would immediately send legitimate Router Advertisements to counter the effects of the Rogue Router Advertisements, such as providing hosts with more preferred prefixes. In addition to protocol-level tools, administrators can monitor the network for the presence of Rogue Router Advertisements and then initiate actions such as blacklisting hosts sending Rogue Router Advertisements. For a full toolbox please see RFC 6104 [65] and RFC 6105 [67]. 3.4.2 Parameter Discovery The Router Advertisement message that nodes receive contains the set of information that nodes need for global communications (link-local communications do not require Router Advertisement, or the presence of routers). The mandatory set of parameter information that may be received via Router Adver- tisements is the following: Hop Limit: The default value that nodes should use in the Hop Limit field of packets they send [41]. Address Autoconfiguration Protocol bit (M-bit): Indicates whether Stateful Address Autoconfiguration (Section 3.5.2) services are available on the link (and that the router knows about it) [41]. Other Configuration Available bit (O-bit): Indicates whether other configuration information is available with Stateless DHCPv6 (and that the router knows it) (Section 3.5.2) [41]. Introduction to IPv6 Home Agent bit: Indicates whether the router sending the Router Advertisement is acting as a Mobile IPv6 home agent [35]. Default Router Preference bits: Indicate the relative preference of the router over other default routers on the same link - see more in Section 3.5.6 and [68]. Router Lifetime: Indicates how long the router can be used for as a default router, and if at all (lifetime value of zero in