[44net] gateways without subnets

Lately I see a number of gateways that are registered without subnets, but still they send traffic. When tracing it, it appears to be usually traffic like MikroTik neighbor discovery. It gets logged in our firewall because it is IP-encap traffic coming from an address that is not in the IP-encap routing table.  And it isn't in the IP-encap routing table because that gateway does not have subnets. Would it be an idea to not send the RIP announcements to gateways without a registered subnet? It would not be useful to them anyway, I think. Rob