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IPv6 Anycast

EdTheLad

So who can tell me what an anycast address is?
Whats the difference between an anycast address and a unicast address i've assigned to multiple hosts.On Cisco i specify anycast after the address in the cli, what does this actually do? Routing will choose the best path to a remote subnet and hence my nearest host, is this just a new term created for the sake of it?

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Comments

Slowhand

From my reading on the subject, anycast looks like multicast except that the first recipient of your anycast message to respond back to you is the winner. . . and that's the host you set up communication with. In theory, this should be the closest host to you.

As for what it's used for, beats me. The Wikipedia entry has a couple of examples, but they're kind of broad and generalized.

EdTheLad

An anycast address is assigned from the global address space.You would use it for something like dhcp, the question is why specify a subnet as being anycast on a cisco router. What does the anycast command do?
I can do exactly the same thing with ipv4, if i advertise the same subnet from two different locations within my network, play with costings so that there is never an equal cost path for both subnets, one will always be preferred, and packets will be forwarded to the closest subnet.

yuriz43

It will disables Duplicate Address Detection and prevent that address from ever being used as the source address for an ipv6 packet.

Met44

EdTheLad wrote: »

Whats the difference between an anycast address and a unicast address i've assigned to multiple hosts.

One difference is how such hosts would behave if they were on the same subnet.