![]() ![]() Bugfix Failure browsing folders in "Online" connect mode (Google Drive & OneDrive, Windows).IPv6 is coming, or so “they” keep telling me.Download Installer (Windows) Download MSI Package (Windows) Download MSI Package Shell Extension for 32bit applications (Windows) Download MSI Package Shell Extension for 64bit applications (Windows) If I ever work on a real world IPv6 network and real world problems, I’ll cover them too. So, that is my start with a lab that breaks IPv6 and takes a look at the problem on the wire using Wireshark. I am hoping to get a chance to dig deeper into IPv6 and other issues as I go with my studies. Sending 5, 1281-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 16/32/64 ms Sending 5, 1280-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 16/34/84 ms Sending 5, 1200-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Sending 5, 1500-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Success rate is 100 percent (5/5), round-trip min/avg/max = 16/44/120 ms Sending 5, 100-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Permit icmp any any (28 matches) sequence 20 I can see this being a troubleshooting nightmare if IPv6 and ICMPv6 is not understood.īack to denying the ‘packet-too-big’ messages:ĭeny icmp any any packet-too-big (10 matches) sequence 10 On a final note, if the ‘packet-too-big’ messages are blocked, this would still allow smaller packets to go through just fine, but your larger packets would not make it. There’s no ‘packet-too-big’ packet anymore because R1 knows that the MTU is only 1280 via the first ‘packet-too-big’ message. Success rate is 100 percent (5/5), round-trip min/avg/max = 24/46/96 ms Now run the test again, and see what is on Wireshark: I assume that stands for packet-too-big, and so let’s take a look at the Wireshark now: Permit icmp any any (14 matches) sequence 20īonus – we even got a new character in that ping output above. Permit icmp any any packet-too-big (5 matches) sequence 10 Success rate is 60 percent (3/5), round-trip min/avg/max = 28/46/64 ms Let’s change up that ipv6 access-list to let them through and see the difference: Great, so now we need to let those ICMP ‘packet-too-big’ messages flow, or we are not going to get any traffic across our new and better-than-sliced-bread IPv6 network… Permit icmp any any (10 matches) sequence 20 You can see the icmpv3 packet-too-big messages being blocked with the ipv6 acl:ĭeny icmp any any packet-too-big (9 matches) sequence 10 Sending 5, 1510-byte ICMP Echos to 2323:2222::3, timeout is 2 seconds: Start a ping on R1 destined for R3 with size set to 1510 for good measure ‘R1#ping 2323:2222::3 size 1510’.Set the ‘R2(config-if)# ipv’ on the interface between R2 R3.Get a little help from an ipv6 access-list and ipv6 traffic-filter on R1 to block the packet-too-big messages.This is an easy setup I think this lab (configs at the end of the post) will show me what I want to see. ![]() ![]() The journey begins to see this packet in Wireshark. Having IPv6 hosts handle packet fragmentation saves IPv6 router processing resources and helps IPv6 networks run more efficiently.” (To see where the quote is from and more information about PMTUD, click here.) In IPv6, however, fragmentation is handled by the source of a packet when the path MTU of one link along a given data path is not large enough to accommodate the size of the packets. “As in IPv4, path MTU discovery in IPv6 allows a host to dynamically discover and adjust to differences in the MTU size of every link along a given data path. ![]() I came across a question with the answer being “Packet Too Big” message is sent back to the source. This “Packet Too Big message” is part of the Path MTU Discovery mechanism, and is vital to IPv6 sending packets now that fragmentation happens at the IPv6 host and is not done by the router. I’m studying for my CCIE R&S written again, as my 2 lab attempts have not gone so well. But this is my start, and maybe it will help somebody else get started also. This is by no means an in-depth look into IPv6 or ICMPv6, and I still have a lot more to learn. Is it or isn’t it? Will it be or won’t it be? When it will be and just get ready for it. So here I go. ![]()
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