Hi everyone.
My isp use dual stack ipv6, but some hardware(ex.android) have ipv6 fallback.
Routeros can do it like the following solution directly on the routing system?
Or have a better solution?
tks 
Default ：IPV6 → Fail → IPV4
Change：IPV4 → Fail → IPV6
Windows solution：
C:>netsh interface ipv6 show prefixpolicies
正在查詢使用中的狀態…
優先順序 標籤 首碼
50 0 ::1/128
40 1 ::/0
30 2 2002::/16
20 3 ::/96
10 4 ::ffff:0:0/96
5 5 2001::/32
C:>netsh interface ipv6 set prefixpolicy ::ffff:0:0/96 100 4
確定。
C:>netsh interface ipv6 show prefixpolicies
正在查詢使用中的狀態…
優先順序 標籤 首碼
100 4 ::ffff:0:0/96
50 0 ::1/128
40 1 ::/0
30 2 2002::/16
20 3 ::/96
5 5 2001::/32
C:>
>
Linux solution：
> ```text
~]# cat /etc/gai.conf
# Label
# Add another rule to the RFC 3484 label table. See section 2.1 in
# RFC 3484.
# The default is:
label ::1/128 0
label ::/0 1
label 2002::/16 2
label ::/96 3
label ::ffff:0:0/96 4
label fec0::/10 5
label fc00::/7 6
#
# Precedence
# Add another rule the to RFC 3484 precedence table. See section 2.1
# and 10.3 in RFC 3484.
# The default is:
precedence ::1/128 50
precedence ::/0 40
precedence 2002::/16 30
precedence ::/96 20
#precedence ::ffff:0:0/96 10
#
# For sites which prefer IPv4 connections change the last line to
precedence ::ffff:0:0/96 100
~]# shutdown -r now