[Kea-users] Lease allocation on option 82

[Bjørn Skovlund]

Hi again,

I haven't debugged the logic completely, but it seems a bit inconsistent.

If I have two DHCP servers in HA mode, using flex-id to map to client-id
with a value that's the same for two clients, they will get a lease each -
one from each server I believe. Whichever one last did the REQUEST, will be
the only entry in the database, as the client-id is the same.

What I was hoping to get to, is that a specific client-id can only ever
take up one IP, which the client changing hwaddr will result in being
offered the same IP as the client-id had with the first hwaddr. Is this a
possibility?

Would an active-standby scenario work better for this use-case?

Config for test bed is attached below:
{
    "Dhcp4": {
        "control-socket": {
            "socket-name": "/opt/run/kea-dhcp4/kea.socket",
            "socket-type": "unix"
        },
        "dhcp-ddns": {
            "enable-updates": false
        },
        "expired-leases-processing": {
            "flush-reclaimed-timer-wait-time": 25,
            "hold-reclaimed-time": 3600,
            "max-reclaim-leases": 100,
            "max-reclaim-time": 250,
            "reclaim-timer-wait-time": 10,
            "unwarned-reclaim-cycles": 5
        },
        "hooks-libraries": [
            {
                "library": "/usr/local/lib/hooks/libdhcp_lease_cmds.so",
                "parameters": {}
            },
            {
                "library": "/usr/local/lib/hooks/libdhcp_host_cmds.so",
                "parameters": {}
            },
            {
                "library": "/usr/local/lib/hooks/libdhcp_legal_log.so",
                "parameters": {
                    "base-name": "kea-forensic4",
                    "path": "/var/kea/log"
                }
            },
            {
                "library": "/usr/local/lib/hooks/libdhcp_flex_id.so",
                "parameters": {
                    "identifier-expression": "relay4[9].hex",
                    "replace-client-id": true
                }
            },
            {
                "library": "/usr/local/lib/hooks/libdhcp_ha.so",
                "parameters": {
                    "high-availability": [
                        {
                            "heartbeat-delay": 1000,
                            "max-ack-delay": 5000,
                            "max-response-delay": 10000,
                            "max-unacked-clients": 0,
                            "mode": "load-balancing",
                            "peers": [
                                {
                                    "name": "dhcp-01.test.site.fastspeed.dk
",
                                    "role": "primary",
                                    "url": "http://172.16.1.2:8079"
                                },
                                {
                                    "name": "dhcp-02.test.site.fastspeed.dk
",
                                    "role": "secondary",
                                    "url": "http://172.16.1.3:8079"
                                }
                            ],
                            "sync-timeout": 60000,
                            "this-server-name": "
dhcp-02.test.site.fastspeed.dk"
                        }
                    ]
                }
            }
        ],
        "host-reservation-identifiers": [
            "client-id"
        ],
        "hosts-database": {
            "host": "snip",
            "name": "kea",
            "password": "snip",
            "type": "mysql",
            "user": "kea"
        },
        "interfaces-config": {
            "dhcp-socket-type": "udp",
            "interfaces": [
                "*"
            ]
        },
        "lease-database": {
            "host": "snip",
            "name": "kea",
            "password": "snip",
            "type": "mysql",
            "user": "kea"
        },
        "match-client-id": true,
        "next-server": "0.0.0.0",
        "option-data": [
            {
                "data": "8.8.8.8, 8.8.4.4",
                "name": "domain-name-servers"
            }
        ],
        "rebind-timer": 600,
        "renew-timer": 300,
        "subnet4": [
            {
                "id": 1684209664,
                "option-data": [
                    {
                        "data": "100.99.0.1",
                        "name": "routers"
                    },
                    {
                        "data": "8.8.8.8, 8.8.4.4",
                        "name": "domain-name-servers"
                    },
                    {
                        "data": "172.16.1.3",
                        "name": "dhcp-server-identifier"
                    }
                ],
                "pools": [
                    {
                        "client-class": "HA_dhcp-01",
                        "pool": "100.99.0.2 - 100.99.0.247"
                    },
                    {
                        "client-class": "HA_dhcp-02",
                        "pool": "100.99.0.248 - 100.99.1.238"
                    }
                ],
                "subnet": "100.99.0.0/23"
            }
        ],
        "valid-lifetime": 1200
    }
}


On Thu, May 2, 2019 at 2:44 PM Bjørn Skovlund <skovlund at gmail.com> wrote:

> Hi Francis,
>
> Thanks for the prompt reply!
>
> On Thu, May 2, 2019 at 12:48 PM Francis Dupont <fdupont at isc.org> wrote:
>
>> > It seems this would be possible with a host reservation on the
>> client-id,
>>
> > but I'm trying to avoid having to copy the lease information into host
>> > reservations.
>>
>> => host reservations are of course the only way to really reserve an
>> address.
>> But you can play with lifetime and expired-leases-processing timers to
>> make more likely a client to get the same IP address.
>>
>
> I'm not that concerned about getting the same IP, but more concerned about
> not handing out multiple addresses to the same client-id.
>
> I think my problem, and misunderstanding of the client-id when it comes to
> lease allocation, may stem from having an active-active HA setup. It seems
> I am limited to two IP addresses, one from each of the servers. It could
> look a bit like my replication of IP addresses broke when I enabled the
> flex-id.
>
> I'll have a closer look at those.
>
> Thanks for your help.
>
> Best, Bjorn
>
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