ICMP Type 3 (code 4)
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Does anyone know if I enable ICMP Type 3 (destination unreachable) on my WAN with pfsense, does this also allow ICMP Fragmentation Needed (Type 3, Code 4) to ensure that Path MTU Discovery works?
There isn't a specific selection for ICMP fragmentation so I assume, allowing Type 3 also allows all the subcodes of that type;
Meaning all below subtypes of Type 3 besides Fragmentation Needed;0 Network Unreachable - The destination network cannot be reached. 1 Host Unreachable - The destination host cannot be reached. 2 Protocol Unreachable - The protocol (e.g., TCP, UDP) is not supported at the destination. 3 Port Unreachable - The port is not accessible at the destination host (often seen with UDP). 4 Fragmentation Needed and DF Set - Packet fragmentation is required, but the DF (Don't Fragment) flag is set. 5 Source Route Failed - Source routing failed along the path to the destination. 6 Destination Network Unknown - The destination network is unknown. 7 Destination Host Unknown - The destination host is unknown. 8 Source Host Isolated - The source host is isolated. 9 Communication with Destination Network is Administratively Prohibited - Network is restricted by administrative policies. 10 Communication with Destination Host is Administratively Prohibited - Host is restricted by administrative policies. 11 Network Unreachable for Type of Service - The network is unreachable for the specified Type of Service (ToS). 12 Host Unreachable for Type of Service - The host is unreachable for the specified ToS. 13 Communication Administratively Prohibited - General administrative restriction (broader than codes 9 and 10). 14 Host Precedence Violation - Indicates a violation of host precedence. 15 Precedence Cutoff in Effect - The precedence of the packet is below the cutoff level.Is my assumption correct?
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I like to know this to!
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@Gerard64 Plus 1 as the kids, say
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I also need to know this. I wish it was just available as an ICMP Subtype in the GUI's Firewall > Rules.
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yeah it could be clearer in the GUI. But basically Type 3 covers all the subtype's codes the OP mentions, including re: fragmentation.
More info on the subtypes can be found online but the IANA site has a very good page on it: https://www.iana.org/assignments/icmp-parameters/icmp-parameters.xhtml
