[Cerowrt-devel] dnsmasq ipv6 stuff

[Phil Pennock]

On 2013-01-22 at 19:14 -0500, Chris Lawrence wrote:
> True, although I think that's pretty much unavoidable given the design
> of ipv6 though (isn't ::1 always the router for the subnet)?

No, the router can have any IP within that subnet, but it will also join
various multicast groups.

Link-local multicast is ff02:: and the ::2 address is "all routers", so
given "se00" as a network device name:

 ping6 ff02::2%se00

should elicit a response from every device on the LAN connected to
CeroWRT's first LAN interface, where the device thinks that it's a
router.

Within the multicast assignments (ff0X::) ::1 is all nodes, so

 ping6 ff02::1%se00

gets a response from every machine which has IPv6 configured up,
assuming no packet filters.

This is defined for ff0X for X with 1, 2 and 5 (interface-local (ie,
this machine), link-local and site-local).  Fortunately, IPv6 doesn't
define this for the global scope, ff0e::, otherwise there would be a
teensy amplification factor for a response to a spoofed ICMP source
address sending a ping to ff0e::1.

For CeroWRT and debugging, the other interesting address in ff02:: (so
you need the %device scoping control on the address) is ff02::1:2 for
All_DHCP_Relay_Agents_and_Servers.

-Phil