Victor Sudakov <v...@mpeks.tomsk.su> wrote in <20190906035608.ga45...@admin.sibptus.ru>:
va> Hiroki Sato wrote: va> > va> Can any IPv6 unicast or link-local address be configured as an anycast va> > va> address of a router? va> > va> > Yes. There is no restriction about address scope. va> > va> > You might want to read RFC 4291, which defines Subnet-Router anycast va> > address, and RFC 2526, which defines the other reserved IPv6 subnet va> > anycast addresses. In general, the former one can be used for va> > routing purpose. va> va> Interestingly, RFC4291 says that "All routers are required to support va> the Subnet-Router anycast addresses for the subnets to which they have va> interfaces." In practice, I don't observe this. A FreeBSD router does va> not configure such an address automatically, for example. They will be automatically configured when an ipv6_prefix_IF rc.conf(5) variable is used to configure a prefix: ----(from rc.conf(5) man page)---- ipv6_prefix_ed0="2001:db8:1:0 2001:db8:2:0" is equivalent to the following: ifconfig_ed0_alias0="inet6 2001:db8:1:: eui64 prefixlen 64" ifconfig_ed0_alias1="inet6 2001:db8:1:: prefixlen 64 anycast" ifconfig_ed0_alias2="inet6 2001:db8:2:: eui64 prefixlen 64" ifconfig_ed0_alias3="inet6 2001:db8:2:: prefixlen 64 anycast" These Subnet-Router anycast addresses will be added only when ipv6_gateway_enable is YES. ---------------------------------- va> RFC2526 is dim, I think it's because of this RFC the last usable address va> on a subnet ends in ff7f instead of ffff. I wonder if anyone anywhere va> uses those subnet anycast addresses. That is because there are few practical applications of the IPv6 anycast address other than failover across multiple routers. -- Hiroki
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