how can i stop my router sending out Destination host unreachable?
in cisco it would be
no ip unreachables
http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/Filter#Properties
icmp-options (integer:integer; Default: ) Matches ICMP type:code fileds
http://wiki.mikrotik.com/wiki/Manual:IP/Firewall/Filter#Chains
There are three predefined chains, which cannot be deleted:
input - used to process packets entering the router through one of the interfaces with the destination IP address which is one of the router’s addresses. Packets passing through the router are not processed against the rules of the input chain
forward - used to process packets passing through the router
output - used to process packets originated from the router and leaving it through one of the interfaces. Packets passing through the router are not processed against the rules of the output chain
http://www.iana.org/assignments/icmp-parameters
/ip firewall filter
add chain=output icmp-options=3:0-255 action=drop
add chain=forward icmp-options=3:0-255 action=drop
Whether you cover just output, just forward, or both depends on whether you want to stop the router from sending out unreachables, from routing unreachables, or both. The Cisco equivalent would be to only drop in the output chain.