In the previous demonstration, the Globomantics client tried to web into the
Wired Brain Coffee server using HTTP, which is not allowed per our security
policy. Specifically, it was denied by an IPv6 access list applied to filter
undesirable traffic. TCP port 80 is not allowed.
The firewall notifies the sender that the packet was denied using the
unreachable shown. Like the port unreachable message we saw earlier when
examining the IPv6 traceroute packets, this message uses type 1. To identify
itself as an admin prohibited message, code 1 is used here. And like all good
unreachables, it encapsulates the offending packet so that the sender knows
which of its processes was responsible.
This is why the Telnet attempt failed right away during the demonstration.
We've reached the end of the final module. We've covered a lot of ground
here. First, I hope it's clear that IPv4 and IPv6 ICMP share much in common,
especially as it relates to the applicability of their messages and tools.
Administrators skilled with IPv4 should find themselves right at home with
IPv6 on these topics.
In my experience, the number one sticking point for IT engineers new to
IPv6 is working with neighbor discovery. It will boost your IPv6
confidence big time once mastery is achieved.
Finally, I want to extend my sincere gratitude to you for
viewing this course. Feel free to contact me on Twitter
with any questions you have. Thank you.