How does IOS choose what IPv6 source address to use?

[DJX995]

I have a 3750X with IOS 15.2.2E.

I have multiple IPv6 addresses on the default VLAN (VLAN 1):

ipv6 address 2001:470:...../64
ipv6 address 2001:470:...../64
ipv6 address 2605:A000:..../64

I have one default IPv6 route:

ipv6 route ::/0 Vlan1 FE80::.....

S   ::/0 [1/0]
     via FE80::....., Vlan1

My question is: when I issue a ping from the 3750X, how does the switch choose what source address to use?

Currently, it seems to use the 2605:A000 address, but why?

Can I change this behavior?

Thanks!

[Peter Koltl]

RFC 6724

[DJX995]

OK,

How about my second question: Can I change this behavior in IOS?

Thanks!