What is the use-case of including the IPv4 address in IPv6 address?

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It is possible to include the IPv4 address into IPv6 address. For example, 2001:db8::c0a8:6301 where last 32 bits are IPv4 address 192.168.99.1. There is even a special notation of IPv6 address where last 32 bits are in dot-decimal notation. Example from Juniper router:



root@mx> show configuration interfaces ge-0/0/0 unit 0 family inet6
address 2001:db8::192.168.99.1/64;

root@mx>


Under which circumstances it makes sense to include the IPv4 address into IPv6 address? Has anyone seen this in practice?






ipv6 ip-address







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    up vote
    3
    down vote

    favorite












    It is possible to include the IPv4 address into IPv6 address. For example, 2001:db8::c0a8:6301 where last 32 bits are IPv4 address 192.168.99.1. There is even a special notation of IPv6 address where last 32 bits are in dot-decimal notation. Example from Juniper router:



    root@mx> show configuration interfaces ge-0/0/0 unit 0 family inet6
    address 2001:db8::192.168.99.1/64;

    root@mx>


    Under which circumstances it makes sense to include the IPv4 address into IPv6 address? Has anyone seen this in practice?






    ipv6 ip-address







    share|improve this question























      up vote
      3
      down vote

      favorite









      up vote
      3
      down vote

      favorite











      It is possible to include the IPv4 address into IPv6 address. For example, 2001:db8::c0a8:6301 where last 32 bits are IPv4 address 192.168.99.1. There is even a special notation of IPv6 address where last 32 bits are in dot-decimal notation. Example from Juniper router:



      root@mx> show configuration interfaces ge-0/0/0 unit 0 family inet6
      address 2001:db8::192.168.99.1/64;

      root@mx>


      Under which circumstances it makes sense to include the IPv4 address into IPv6 address? Has anyone seen this in practice?






      ipv6 ip-address







      share|improve this question













      It is possible to include the IPv4 address into IPv6 address. For example, 2001:db8::c0a8:6301 where last 32 bits are IPv4 address 192.168.99.1. There is even a special notation of IPv6 address where last 32 bits are in dot-decimal notation. Example from Juniper router:



      root@mx> show configuration interfaces ge-0/0/0 unit 0 family inet6
      address 2001:db8::192.168.99.1/64;

      root@mx>


      Under which circumstances it makes sense to include the IPv4 address into IPv6 address? Has anyone seen this in practice?






      ipv6 ip-address




      ipv6 ip-address






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      asked 3 hours ago









      Martin

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          There are some common use cases:




          • ::ffff:192.168.0.1



            This is used in software that uses IPv6 sockets even for handling IPv4 connections. That makes it easier to write software because everything looks like IPv6.




          • 64:ff9b::192.168.0.1



            This is the NAT64 well-known-prefix. These addresses are NATed to IPv4 by a NAT64 gateway. It is used to let devices that only have IPv6 reach IPv4 destinations.



          It can be used with other prefixes as well. For example not all NAT64 gateways use the well-known-prefix. And there are other protocols that embed IPv4 addresses in IPv6 addresses or prefixes. The two mentioned above are the most common though.






          share|improve this answer
















          • 1




            Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
            – Michael Hampton
            1 hour ago










          • Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
            – Martin
            1 min ago










          Your Answer








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          up vote
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          There are some common use cases:




          • ::ffff:192.168.0.1



            This is used in software that uses IPv6 sockets even for handling IPv4 connections. That makes it easier to write software because everything looks like IPv6.




          • 64:ff9b::192.168.0.1



            This is the NAT64 well-known-prefix. These addresses are NATed to IPv4 by a NAT64 gateway. It is used to let devices that only have IPv6 reach IPv4 destinations.



          It can be used with other prefixes as well. For example not all NAT64 gateways use the well-known-prefix. And there are other protocols that embed IPv4 addresses in IPv6 addresses or prefixes. The two mentioned above are the most common though.






          share|improve this answer
















          • 1




            Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
            – Michael Hampton
            1 hour ago










          • Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
            – Martin
            1 min ago














          up vote
          4
          down vote













          There are some common use cases:




          • ::ffff:192.168.0.1



            This is used in software that uses IPv6 sockets even for handling IPv4 connections. That makes it easier to write software because everything looks like IPv6.




          • 64:ff9b::192.168.0.1



            This is the NAT64 well-known-prefix. These addresses are NATed to IPv4 by a NAT64 gateway. It is used to let devices that only have IPv6 reach IPv4 destinations.



          It can be used with other prefixes as well. For example not all NAT64 gateways use the well-known-prefix. And there are other protocols that embed IPv4 addresses in IPv6 addresses or prefixes. The two mentioned above are the most common though.






          share|improve this answer
















          • 1




            Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
            – Michael Hampton
            1 hour ago










          • Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
            – Martin
            1 min ago












          up vote
          4
          down vote










          up vote
          4
          down vote









          There are some common use cases:




          • ::ffff:192.168.0.1



            This is used in software that uses IPv6 sockets even for handling IPv4 connections. That makes it easier to write software because everything looks like IPv6.




          • 64:ff9b::192.168.0.1



            This is the NAT64 well-known-prefix. These addresses are NATed to IPv4 by a NAT64 gateway. It is used to let devices that only have IPv6 reach IPv4 destinations.



          It can be used with other prefixes as well. For example not all NAT64 gateways use the well-known-prefix. And there are other protocols that embed IPv4 addresses in IPv6 addresses or prefixes. The two mentioned above are the most common though.






          share|improve this answer












          There are some common use cases:




          • ::ffff:192.168.0.1



            This is used in software that uses IPv6 sockets even for handling IPv4 connections. That makes it easier to write software because everything looks like IPv6.




          • 64:ff9b::192.168.0.1



            This is the NAT64 well-known-prefix. These addresses are NATed to IPv4 by a NAT64 gateway. It is used to let devices that only have IPv6 reach IPv4 destinations.



          It can be used with other prefixes as well. For example not all NAT64 gateways use the well-known-prefix. And there are other protocols that embed IPv4 addresses in IPv6 addresses or prefixes. The two mentioned above are the most common though.







          share|improve this answer












          share|improve this answer



          share|improve this answer










          answered 1 hour ago









          Sander Steffann

          5,7601126




          5,7601126







          • 1




            Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
            – Michael Hampton
            1 hour ago










          • Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
            – Martin
            1 min ago












          • 1




            Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
            – Michael Hampton
            1 hour ago










          • Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
            – Martin
            1 min ago







          1




          1




          Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
          – Michael Hampton
          1 hour ago




          Then there are the network admins who manually assign IPv6 addresses that have the host-part equal to the host's IPv4 address....
          – Michael Hampton
          1 hour ago












          Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
          – Martin
          1 min ago




          Thanks! Is there a valid use-case to manually assign IPv6 addresses that have the host-part equal to the hosts IPv4 address? I can clearly see a benefit of using the penultimate byte of the IPv4 address in IPv6 address network portion(this works only in case of /24 IPv4 networks), but I hardly see a benefit of putting the IPv4 address into host-portion of the IPv6 address. Even if there are multiple IPv4 addresses on the interface(for example 192.0.2.22/24 and 192.0.2.25/24) and same amount of IPv6 addresses are needed, then it would make sense to take those from the beginning of the network.
          – Martin
          1 min ago

















           

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