13-13Configuring Parameters Related to RA MessagesYou can enable an interface to send RA messages, and configure the interval for sending RAmessages and parameters in RA messages. After receiving an RA message, a host can use theseparameters to perform corresponding operations. Table 13-4 lists the configurable parameters in an RAmessage and their descriptions.Table 13-4 Parameters in an RA message and their descriptionsParameters DescriptionCur hop limitWhen sending an IPv6 packet, a host uses the value to fill the Cur HopLimit field in IPv6 headers. The value is also filled into the Cur Hop Limitfield in response messages of a device.Prefix informationoptionsAfter receiving the prefix information advertised by the device, the hosts onthe same link can perform stateless autoconfiguration.M flagThis field determines whether hosts use the stateful autoconfiguration toacquire IPv6 addresses.If the M flag is set to 1, hosts use the stateful autoconfiguration to acquireIPv6 addresses (for example, through a DHCP server). Otherwise, hostsuse the stateless autoconfiguration to acquire IPv6 addresses, that is,hosts generate IPv6 addresses according to their own link-layer addressesand the prefix information issued by the router.O flagThis field determines whether hosts use the stateful autoconfiguration toacquire information other than IPv6 addresses.If the O flag is set to 1, hosts use the stateful autoconfiguration to acquireinformation other than IPv6 addresses (for example, through a DHCPserver). Otherwise, hosts use the stateless autoconfiguration to acquireinformation other than IPv6 addresses.Router lifetimeThis field is used to set the lifetime of the router that sends RA messagesto serve as the default router of hosts. According to the router lifetime inthe received RA messages, hosts determine whether the router sendingRA messages can serve as the default router.Retrans timer If the device fails to receive a response message within the specified timeafter sending an NS message, the device will retransmit the NS message.Reachable timeIf the neighbor reachability detection shows that a neighbor is reachable,the device considers the neighbor reachable within the specified reachabletime. If the device needs to send a packet to a neighbor after the specifiedreachable time expires, the device will reconfirm whether the neighbor isreachable.The values of the Retrans Timer and the Reachable Time configured for an interface are sent to hostsvia RA messages. Furthermore, this interface sends NS messages at the interval of Retrans Timer andconsiders a neighbor reachable within the Reachable Time.Follow these steps to configure parameters related to an RA message:To do… Use the command… RemarksEnter system view system-view —
