Error code 2 ICMP - IPV6

[PietroPoliseno27977]

Hi everyone what does error code 2 mean in the ipv6 version? On the ietf website there is write this: If the reason for the failure to deliver is that the destination is beyond the scope of the source address, the Code field is set to 2. This condition can occur only when the scope of the source address is smaller than the scope of the destination address (e.g., when a packet has a link-local source address and a global-scope destination address) and the packet cannot be delivered to the destinati without leaving the scope of the source address. But there is no example to make it better understood even on the net Can anyone give some examples?

[Seb Rupik · Accepted solution]

Hi there,

Originally IPv6 had the following scopes specified: link-local, site-local and global. At this point in time only link-local and global scopes exist as site-local has been depreciated.

The scope of an address determines the area over which it is uniquely routable. Therefore a link-local address is unique amongst the hosts which are connected to the same network segment and an address in the global scope should be globally unique and routable. NB, a hosts loopback interface should be considered as within the link-local scope.

As RFC4443 which you quote from states, traffic sourced from an address within one scope cannot communicate with a destination address in another scope, ie:

fe80::1/64  cannot communicate with 2001:630:d0:f000::1/64

fe80::1/64 can communicate with fe80::2/64

2001:630:d0:f000::1/64 can communicate with 2001:d0:f100::1/64

These ICMP error messages are generated by the first hop router which receives these forbidden inter-scope communications.

cheers,

Seb.