CCNA Introduction to Networks: ICMPv4 & ICMPv6 Destination Unreachable Codes Practice.

For ICMPv4, what does code “0” mean?

Net Unreachable

For ICMPv4, What code does “1” mean?

Host Unreachable

For ICMPv4, what code does “2” mean?

Protocol Unreachable

For ICMPv4, what code does “3” mean?

Port Unreachable (ICMPv4)

For ICMPv6, what does the code “0” mean?

No route to destination.

For ICMPv6, what does the code “1” mean?

Communication with the destination is administratively prohibited.

For ICMPv6, what does the code “2” mean?

Beyond scope of the source address

For ICMPv6, what does the code “3” mean?

Address Unreachable

For ICMPv6, what does the code “4” mean?

Port Unreachable (ICMPv6)

Why would ICMPv6 send a “Time Exceeded” message?

When the router cannot forward an IPv6 packet because the packet has expired.

Why would ICMPv4 send a “Time Exceeded” message?

Because the Time-to-Live (TTL) field of the packet was decremented to 0.