Concepts
Preference of an IP address
Every IP address advertised in RAs has a preference value. The IP address with the highest preference is selected as the default router address.
You can configure the preference for IP addresses advertised on a router interface.
The bigger the preference value, the higher the preference. The minimum preference value (-2147483648) is used to indicate that the address, even though it may be advertised, is not to be used by neighboring hosts as a default router address.
Lifetime of an IP address
An RA contains a lifetime field that specifies the lifetime of advertised IP addresses. If no new RA for an IP address is received within the lifetime of the IP address, the host removes the corresponding route information.
All the IP addresses advertised by an interface have the same lifetime.
Advertising interval
A router interface with IRDP enabled sends out RAs at a random interval between the minimum advertising interval and the maximum advertising interval. This mechanism prevents the local link from being overloaded by a large number of RAs sent simultaneously from routers.
HP recommends shortening the advertising interval on a link that suffers high packet loss rates.
Destination address of RAs
An RA uses either of the two destination IP addresses:
broadcast address 255.255.255.255.
Multicast address 224.0.0.1, which identifies all the hosts on the local subnet.
By default, the destination IP address of an RA is the broadcast address. If the interface that sends RAs supports multicast, configure 224.0.0.1 as the destination IP address.
Proxy-advertised IP addresses
By default, an interface advertises its primary IP address and manually configured secondary IP addresses. You can configure other IP addresses for an interface to proxy-advertise.