According to Cisco: “An anycast address is an address that is assigned to a set of interfaces that typically belong to different nodes. A packet sent to an anycast address is delivered to the closest interface (as defined by the routing protocols in use) identified by the anycast address. Anycast addresses are syntactically indistinguishable from unicast addresses, because anycast addresses are allocated from the unicast address space. Assigning a unicast address to more than one interface makes a unicast address an anycast address. Nodes to which the anycast address is assigned must be explicitly configured to recognize that the address is an anycast address.”

According to Wikipedia: “Anycast is a network addressing and routing methodology in which datagrams from a single sender are routed to the topologically nearest node in a group of potential receivers, though it may be sent to several nodes, all identified by the same destination address.”

According to Me: “metode pengalamatan jaringan (network addressing) dan routing jaringan dimana setiap akses pengguna akan di routing menuju titik (node) terdekat dari kumpulan beberapa node yang aktif (one-to-one-of-many).”

Melemparkan akses ke node yang paling dekat…

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Well, berawal dari keingintahuan tentang mengapa IPv6 meninggalkan broadcast dan menggantinya menjadi Anycast, I made this article…hope its helps

Pengganti dari broadcast adalah Multicast dan Anycast, why broadcast disappear in IPv6?? Because not bandwidth friendly and not processor friendly (link)

Multicast…you guys already knows this…

But anycast?…let me give you an example

Klo kita mau internetan…pasti pake DNS (siapa yang mau ngapalin IP address 112.215.88.25 atau 173.252.120.6?!?!)

Apa lagi pake IPv6…mau lu ngapain ip 2a03:2880:2130:cf05:face:b00c:0:1 hanya untuk ke facebook aja?

Untuk itu ada DNSv6 untuk IPv6, nah…Anycast di IPv6 bisa bikin 2 Server DNS punya IPv6 address yang sama persis

Dari arah Router R1…traffic ke DNS akan diarahkan ke SERVER_DNS1, sedangkan dari R3 akan diarahkan ke SERVER_DNS2

Jadi klo interface fa0/0 di R1 yang kearah DNS1 mati…otomatis traffic DNS dari R1 akan diarahkan ke SERVER_DNS2 yang ada di R3

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Anycast Configuration

First…lets do some routing, we use OSPFv3 for all connection

In R1 and R3

The requirement for Anycast is:

  • Pake IPv6 IP Address network (1234::/64) for interface (jgn HOST address kek 1234::1234/64)
  • Defaultnya klo kita pake network address…akan dianggap anycast juga
  • Kenapa dipake juga keyword anycast…untuk bilang ke router secara spesifik address mana yang jadi Anycast

DNS1 and DNS2 you can config on your own like this

See…same IPv6 for those 2 DNS

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Lets verify

Dari R1…kita cek ping dan trace ke 1234::1234

Lets bring Fa0/0 on R1 down

Dan R1 masih bisa ping ke 1234::1234 (lemparnya ke DNS2) in case klo fa0/0 yang ke arah DNS1 down

This is the definition of anycast

Trus kok bisa R1 nganterinnya ke DNS1, ga ke DNS2, anggeplah Fa0/0 nya ga mati?

Remember kids…Anycast is one to NEAREST…what nearest in this term is…metrics of course (OSPF cost in this case)

And that’s folks…the configuration of Anycast

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Reference:

Cbt Nugget IPv6 Video from Keith Barker #6783

http://www.e-tutes.com/lesson5/networking_fundamentals_lesson5_2.htm1