| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Type (9) | 0 (16 for mobile) | ICMP header checksum | |||||||||||||||||||||||||||||
| # addresses | address entry size | lifetime | |||||||||||||||||||||||||||||
| Router Address 1 | |||||||||||||||||||||||||||||||
| Preference Level 1 | |||||||||||||||||||||||||||||||
| Router Address 2 | |||||||||||||||||||||||||||||||
| Preference Level 2 | |||||||||||||||||||||||||||||||
| .... | |||||||||||||||||||||||||||||||
| Router Address k | |||||||||||||||||||||||||||||||
| Preference Level k | |||||||||||||||||||||||||||||||
notes:
# addresses is number of addresses associated with router that are advertised in this message
address entry size # of 32bit words of information included with each address (in the case above, AES=2)
lifetime # seconds that requestor should rely on this advertisement
router address # octet IP address of router
preference level integer preference of address (higher=preferred address)
ICMP header immediately follows IP header
Type Name/Codes (Code=0 unless otherwise specified)
0 Echo Reply 3 Destination Unreachable 0 Net Unreachable 1 Host Unreachable 2 Protocol Unreachable 3 Port Unreachable 4 Fragmentation Needed & DF Set 5 Source Route Failed 6 Destination Network Unknown 7 Destination Host Unknown 8 Source Host Isolated 9 Network Administratively Prohibited 10 Host Administratively Prohibited 11 Network Unreachable for TOS 12 Host Unreachable for TOS 13 Communication Administratively Prohibited 4 Source Quench 5 Redirect Message 0 Redirect Datagram for the Network 1 Redirect Datagram for the Host 2 Redirect Datagram for the TOS & Network 3 Redirect Datagram for the TOS & Host 6 Alternative Host Address 7 Reserved 8 Echo 9 Router Advertisement 10 Router Selection 11 Time Exceeded 0 Time to Live exceeded in Transit 1 Fragment Reassembly Time Exceeded 12 Parameter Problem 0 Pointer indicates the error 1 Missing a Required Option 2 Bad Length 13 Timestamp 14 Timestamp Reply 15 Information Request 16 Information Reply 17 Address Mask Request 18 Address Mask Reply 19 reserved for security 20-29 reserved 30 Traceroute 31-41 various services 42-255 reserved