RE: Doubt in RFC 3484

[Dave Thaler <[e-mail]>]

jiten shah writes: 
> Consider a topology where two routers are connected back to back. these link
> have only a IPv6 link local address. I want to ping a global address on the
> other switch through this link. RFC 3484 says that for  selecting the source
> address :
> 
>  It is RECOMMENDED that the candidate source addresses be the set of
>    unicast addresses assigned to the interface that will be used to send
>    to the destination.  (The "outgoing" interface.)  On routers, the
>    candidate set MAY include unicast addresses assigned to any interface
>    that forwards packets, subject to the restrictions described below.
[...]
> 
> So since in my topology the outgoing link does not have a global v6 address I
> need to use address on other interface but I do not understand the above
> condition. Can someone simplify it on what basis we can use the addresses
> on the other interface ? Can some one please explain me

Since the requirements language is RECOMMENDED and MAY, you're free
to use addresses on other interfaces any time you have a good reason to do so.
Hence it's ok to use a global address from another interface as the source 
address of a ping in the case you describe.

-Dave