[kea-dev] link-local-only operation

[Tomek Mrugalski]

On 15.05.2015 16:56, Templin, Fred L wrote:
> I have a DHCPv6 PD use case where the DHCPv6 server (acting also as a delegating
> router) is always on the same link as the DHCPv6 client (acting also as a requesting
> router). There is therefore no reason that I should have to assign a non-link-local
> address and prefix to the link, since link-local-only would get the job done. But,
> kea does not appear to allow for link-local-only configurations.
> 
> In a configuration like this, it should be possible to tell the kea server to service
> all clients connected to the link even though the link itself does not have a
> non-link-local address and prefix assignment. Much in the same way that you
That is already supported. See Section 8.2.13. Note the "interface"
parameter. For any subnet, you can say that it is reachable over local
interface directly.

If I understand it correctly, you want a configuration that:
- does not assign addresses (IA_NA)
- does assign prefixes (IA_PD)
- is connected directly (not via relays)
- the interface your server connects to your clients has only link-local
address

If my understanding i correct, the following config should address your
needs:

{
"Dhcp6":

{
# Kea is told to listen on eth0 interface only.
  "interfaces-config": {
     "interfaces": [ "eth0" ]
  },

  "lease-database": {
    "type": "memfile"
  },

  "preferred-lifetime": 3000,
  "valid-lifetime": 4000,
  "renew-timer": 1000,
  "rebind-timer": 2000,

# The following list defines a subnet. There's only one subnet
# in this case and it is reachable directly over eth0.
  "subnet6": [.
    {
      "pools": [ ],
      "pd-pools": [
            {
                "prefix": "2001:db8:1::",
                "prefix-len": 56,
                "delegated-len": 64
            }
        ],

# That doesn't really matter. Kea will be unhappy if there's no
# subnet parameter.
      "subnet": "2001:db8::/64",

# This tells kea that this subnet is reachable locally over eth0
      "interface": "eth0"
    }
  ]
}

}

This will cause Kea to communicate over eth0 using link-local addresses
only. It will delegate /64 prefixes out of its 2001:db8:1::/56 pool.
If clients ask for addresses (send IA_NA), they will get NoAddrsAvail in
their IA_NA responses.

Does that address your need?

Tomek