About RA message parameters
You can enable an interface to send RA messages, and configure the interval for sending RA messages and parameters in RA messages. After receiving an RA message, a host can use these parameters to perform corresponding operations. Table 10 describes the configurable parameters in an RA message.
Table 10: Parameters in an RA message and their descriptions
Parameter | Description |
|---|---|
Hop Limit | Maximum number of hops in RA messages. A host receiving the RA message fills the value in the Hop Limit field of sent IPv6 packets. |
Prefix information | After receiving the prefix information, the hosts on the same link can perform stateless autoconfiguration. |
MTU | Guarantees that all nodes on the link use the same MTU. |
M flag | Determines whether a host uses stateful autoconfiguration to obtain an IPv6 address. If the M flag is set to 1, the host uses stateful autoconfiguration (for example, from a DHCPv6 server) to obtain an IPv6 address. Otherwise, the host uses stateless autoconfiguration to generate an IPv6 address according to its link-layer address and the prefix information in the RA message. |
O flag | Determines whether a host uses stateful autoconfiguration to obtain configuration information other than the IPv6 address. If the O flag is set to 1, the host uses stateful autoconfiguration (for example, from a DHCPv6 server) to obtain configuration information other than the IPv6 address. Otherwise, the host uses stateless autoconfiguration. |
Router Lifetime | Tells the receiving hosts how long the advertising router can live. If the lifetime of a router is 0, the router cannot be used as the default gateway. |
Retrans Timer | If the device does not receive a response message within the specified time after sending an NS message, it retransmits the NS message. |
Reachable Time | If the neighbor reachability detection shows that a neighbor is reachable, the device considers the neighbor reachable within the specified reachable time. If the device needs to send a packet to the neighbor after the specified reachable time expires, the device reconfirms whether the neighbor is reachable. |
Router Preference | Specifies the router preference in an RA message. A host selects a router as the default gateway according to the router preference. If router preferences are the same, the host selects the router from which the first RA message is received. |