DDNS - Option 81

[#1]

Hello everyone, I have read multiple post and decided to post separate one just because i need more clarification (Am new to infoblox)

What is the exact use of IPv4 DDNS - Option 81

i have 2 option under option -81

1 - DHCP server always updates DNS

2- DHCP server updates DNS if requested by client

As per my understanding, 1st is for, infoblox will send the DDNS updates to DNS server and 2nd is for, let the DHCP clients register the DDNS directly to DNS server.

Note  - My DNS server and DHCP clients are Windows.

[#2 · Accepted solution]

Hello there,

Option 81 (Client Fully Qualified Domain Name + DDNS update instructions) is data with instructions that are sent from a DHCP client to DHCP server(s).

The following actions are performed based on the Option-81 Configuration.

While Disabled: Ignore client's option-81 data and DDNS update instructions as per the DDNS settings of the DHCP server.

While Enabled :

DHCP server always updates DNS:

Support "Option-81" data, pick domain name & hostname for DDNS updates for that client from the provided option 81 FQDN and the DHCP server always updates DNS disregarding client preferences. (such as a client setting the DDNS 'S' bit to '0', indicating that the server should not perform DDNS - A client sets the bit = 0 to indicate the server SHOULD NOT perform the updates and bit = 1 to indicate the server SHOULD perform the updates).

dhcpd.conf:

deny client-updates;
ddns-domainname = pick ( option fqdn.domainname, "ddns-example.com" );
ddns-hostname = pick ( option fqdn.hostname, option host-name );

DHCP server updates DNS if requested by Client:

Support "Option-81" data, pick domain name & hostname for DDNS updates for that client from the provided option 81 FQDN and the DHCP server updates DNS for that client only if the client requests so.

dhcpd.conf:

allow client-updates;
ddns-domainname = pick ( option fqdn.domainname, "ddns-example.com" );
ddns-hostname = pick ( option fqdn.hostname,option host-name,

For instances, if the Client requests the DHCP server to add its Hostname to a particular domain (by setting the S bit to 1), the DHCP server will accept its request and update accordingly; if not (S bit set to 0), the DHCP server will not update the DNS Forward-Map. But DHCP Server can still update the Reverse-Map if configured to do so.

Hope this helps.

Regards.