This article discuss the support of DHCP Option 81 on SRX devices.
- SRXis acting as a DHCP Server.
- DHCP option 81 “Client FQDN option” is being implemented on the SRX and Clients.
- Intention is to make SRX update the A and PTRrecords on the DNS server, whneevr a Client gets a new IP or IP gets renewed.
- SRX leases out the IP’s as expected.
- The A and PTR records are not being updated on the DNS server by the SRX.
The DHCP option 81 is not supported on the SRX and J series Platforms.
But we have got a method to implement the feature if required.
Understanding DHCP option 81 :
- This option also called the “Client FQDN Option” is used to update DNS servers with A and PTR DNS records when ever end hots either get a new Ip or Ip gets renewed.
- This option needs to be requested by the client in DHCP discover and Request (the flags in the request determine the nature of the request. For details refer :RFC 4702)
- The DHCP Server conveys its capapbility of wether it will perform the DNS update. or not to the clients.
- To perform the DNS update the DHCP server should have the authority on the DNS server to update.
- The DHCP Server if capable always performs the PTR update, the A update can be done either by CLIENT or the SERVER.
The below steps can be impleneted on the on the Active Directory, to get the updates of DNS A and PTR entries.
- On the Domain Controller open: Start Menu -> Administrative Tools -> Group Policy Management
- From within the Group Policy Management Console, right click on the configured domain and choose Create new GPO
- Apply in the new GPO the settings showing the in diagram below.
- Update the Group Policy on all the clients in the domain. (this can be done in several ways, either from cmd or PowerShell