[Kea-users] option 54 in subnet definition

[Igor Smitran]

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"
          },

...