valid lifetime of a prefix
ra_reachabletime integer 0 Reachable Time in milliseconds to be
advertised in RA messages
+ra_retranstime integer 0 Retransmit Time in milliseconds to be
+ advertised in RA messages
ra_hoplimit integer 0 Current hoplimit to be advertised
in RA messages
ra_mtu integer 0 MTU to be advertised in