Comparing ICMPv4 and ICMPv6 Messages
Table 5-3 lists commonly used ICMPv4 messages and their ICMPv6 equivalents listed in order of the ICMPv4 Type and Code fields.
Table 5-3. ICMPv4 Messages and Their ICMPv6 Equivalents
| ICMPv4 Message | ICMPv6 Equivalent |
|---|---|
Destination Unreachable-Network Unreachable (Type 3, Code 0) | Destination Unreachable-No Route to Destination (Type 1, Code 0) |
Destination Unreachable-Host Unreachable (Type 3, Code 1) | Destination Unreachable-Address Unreachable (Type 1, Code 3) |
Destination Unreachable-Protocol Unreachable (Type 3, Code 2) | Parameter Problem-Unrecognized Next Header Type Encountered (Type 4, Code 1) |
Destination Unreachable-Port Unreachable (Type 3, Code 3) | Destination Unreachable-Port Unreachable (Type 1, Code 4) |
Destination Unreachable-Fragmentation Needed and DF Set (Type 3, Code 4) (as specified in RFC 1191) | Packet Too Big (Type 2, Code 0) |
Destination Unreachable-Communication with Destination Host Administratively Prohibited (Type 3, Code 10) | Destination Unreachable-Communication with Destination Administratively Prohibited (Type 1, Code 1) |
Source Quench (Type 4, Code 0) | This message is not present in IPv6. |
Redirect (Type 5, Code 0) | Neighbor Discovery Redirect message (Type 137, Code 0). For more information, see Chapter 6, "Neighbor Discovery." |
Time Exceeded-TTL Exceeded in Transit (Type 11, Code 0) | Time Exceeded-Hop Limit Exceeded in Transit (Type 3, Code 0) |
Time Exceeded-Fragment Reassembly Time Exceeded (Type 11, Code 1) | Time Exceeded-Fragment Reassembly Time Exceeded (Type 3, Code 1) |
Parameter Problem (Type 12, Code 0) | Parameter Problem (Type 4, Code 0 or Code 2) |
The comparisons between the ICMPv4 Destination Unreachable-Network Unreachable and Destination Unreachable-Host Unreachable messages and their IPv6 equivalents are based on the historical definitions of these messages. In common practice, the ICMPv4 Destination Unreachable-Network Unreachable message is not used because in a classless addressing environment, the network of the destination cannot be determined from the destination address. Instead, the ICMPv4 Destination Unreachable-Host Unreachable message is sent when a route is not found for the destination.
