Mark Andrews wrote:
Ensure that the firealls at both ends pass ICMP/ICMPv6 PTB. Only idiots block all ICMP/ICMPv6. Yes there are a lot of idiots in the world.
The worst idiots are people who designed ICMPv6 [RFC2463] as: (e.2) a packet destined to an IPv6 multicast address (there are two exceptions to this rule: (1) the Packet Too Big Message - Section 3.2 - to allow Path MTU discovery to work for IPv6 multicast, and (2) the Parameter Problem Message, Code 2 - Section 3.4 - reporting an unrecognized IPv6 option that has the Option Type highest-order two bits set to 10), or which makes it necessary, unless you are idiots, to filter ICMPv6 PTB against certain packets, including but not limited to, multicast ones. Masataka Ohta