ICMP type 3 Code 4

[jon_fl]

Should I allow ICMP: type 3 code 4? If so, outbound, inbound or both? Are there any security concerns? Thanks. :-\

[ArtLonger]

Inbound.

ICMP Type 3 - Destination Unreachable Message

IP Fields: Destination Address
The source network and address from the original datagram's data.

ICMP Fields: Type 3
Code:
0 = net unreachable;
1 = host unreachable;
2 = protocol unreachable;
3 = port unreachable;
4 = fragmentation needed and DF set;
5 = source route failed.