I am trying to understand the prefixpolicies.
Could somebody explain to me what the table from netsh interface ipv6 show prefixpolicies
means on windows?
Precedence Label Prefix
---------- ----- --------------------------------
50 0 ::1/128
40 1 ::/0
35 4 ::ffff:0:0/96
30 2 2002::/16
5 5 2001::/32
3 13 fc00::/7
1 11 fec0::/10
1 12 3ffe::/16
1 3 ::/96
Above is an example from my laptop. I know that the leftmost column means priority. The higher it is, the more likely that it will be used. I guess the label is just for identifying the different rules.
But why are these specific rules there? I understand that the rule labeled 3 is representing the range the ipv4 addresses cover and I assume that this is rated lowest because then, windows will prefer any available ipv6 connection over its ipv4 counterpart.
And the rule labeled 0 is probably the loopback address.
What are the other rules there for? Why do the addresses starting with 2002
and 2001:0000
have less priority than basically every other address? (Comparing the priority of rules 1, 2, 5)
Edit:::ffff:0:0/96
regards the IPv4-mapped IPv6 addresses as described here
IPv4 address embedding is used to create a relationship between an
IPv4 address and an IPv6 address to aid in the transition from IPv4 to
IPv6. One type, the IPv4-compatible IPv6 address, is used for devices
that are compatible with both IPv4 and IPv6; it begins with 96 zero
bits. The other, the IPv4-mapped address, is used for mapping IPv4
devices that are not compatible with IPv6 into the IPv6 address space;
it begins with 80 zeroes followed by 16 ones.
So that means my windows prefers mapped IPv4 connections over the real IPv4 addresses. Not sure why, just adding this for completeness.
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