This read-write DisplayString holds the IPv6 prefix list of router source addresses that Router Advertisements are allowed to come from, relevant only when rlRaGuardPolicyMatchRaAddrSpecified is true, with an empty string disabling this check. An admin cares because it lets RA Guard whitelist the specific router addresses that should legitimately be sending RAs on a segment, dropping anything else. For example, setting this to the known router's /128 address on policy "raguard-host" causes RA Guard to drop any RA whose source address isn't that router.