[Kea-users] option 54 in subnet definition

[Igor Smitran]

Ok, thanx.
Just wanted to be sure that i didn't misconfigured the server.
So far i have manage to bypass the problem by creating buffer_receive 
and pkt_send hooks.

pkt_send is changing server-id when sent to client (based on some 
conditions).
buffer_receive is changing it back to server private ip. Otherwise the 
packet would be dropped because of foreign identifier error.

Igor

On 12/16/2016 10:45 AM, Francis Dupont wrote:
> We know the address given is server-identifier should get more control,
> there are some tickets about this (and as far as I know no time to
> deal with them soon...).
>
> Regards
>
> Francis Dupont <fdupont at isc.org>
> Igor Smitran writes:
>> Hi list,
>>
>> Did any of you tried to set custom server-identifier in a subnet?
>>
>> In case you wonder why would one do that:
>>
>> Server is in a private network, behind firewall. There is a dhcp relay
>> that forwards all requests to dhcp server.
>>
>> But, when server leases a public ip to a cpe device then cpe device is
>> not able to renew it's lease because it is not able to send unicast
>> packet to dhcp server private ip.
>>
>> Here comes ASA to rescue. There is a NAT on a public ip that forwards
>> all dhcp packets to private ip of dhcp server.
>>
>> So, DHCP server needs to change his server-identifier in order to tell
>> the client that he can renew his lease by using public ip.
>>
>> But, this doesn;t work, server still sends his private IP in option 54.
>>
>>       {    "subnet": "PUBLIC/26",
>>            "renew-timer": 300,
>>            "rebind-timer" : 525,
>>            "pools": [ { "pool": "FIRST_PUBLIC_IP - LAST_PUBLIC_IP" } ],
>>            "option-data" : [
>>            {
>>              "name" : "dhcp-server-identifier",
>>              "code" : 54,
>>              "space" : "dhcp4",
>>              "csv-format" : true,
>>              "data" : "PUBLIC_IP_ASA_NAT"
>>            },
>>
>> ...
>>
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>>
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