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DHCP & DNS Theory Clarification RRS feed

  • Question

  • I'm posting the following, simply to figure out if my understanding of Leasing, Refresh/Register and Scavenging is on the right track.

    Based on the following settings, I have written what I believe is the life-cycle of an IP Lease and Timestamp

    I HAVE AN IMAGE TO GO HERE. It shows the DHCP Scope settings Lease duration set to 8 days. And the DNS Zone settings set to allow scavenging, No-refresh interval 7 days, and Refresh interval 7 days.

    DHCP renews lease every 8 days for a client. DNS does not allow a Client initiated Dynamic Update for 7 days from the Timestamp. Then, allows 7 days of refresh availability, before scavenging is available. This configuration works in the following manner:

    Day 1: DHCP issues an IP and Lease to the client, and registers Client IP and Name with DNS. DNS Timestamp is created.

    Days 2-6: Client attempts to Dynamically Register/Refresh DNS every 24 hours (Default Interval). But, gets refused by DNS.

    Day 7: Clients are able to Dynamically Register/Refresh with DNS, on a 24-hour interval for the next 7 days.

    Day 8: DHCP issues a new Lease (possibly new IP, but likely reuses IP) to client, and registers with DNS.

    DNS creates new Timestamp. This is now day 1 for the Timestamp in DNS. This cycle returns to end of Day 1.

    Summary: After an issuance of an IP Lease, and DNS Timestamp, clients are not able to refresh DNS for 7 days. On the 7th day, clients are able to update with DNS. However, the very next day, DHCP renews the lease and DNS creates a new Timestamp, and the “No-refresh for 7 days” begins again. Days 9 through 14 are never reached by a client. DNS will not scavenge a RR, unless the client gets a different IP from DHCP, and not until day 14.

    This is my theory of why Desktop Events have an entry, once every 24 hours: “The system failed to register host (A or AAAA) resource records (RRs) for network adapter with settings: Adapter Name : {EB1A194E-2EC0-4C9A-B01E-2A712209EC47} Host Name : CLIENT-COMPUTER Primary Domain Suffix : COMPANY.COM DNS server list : 10.100.85.59, 10.100.85.60 Sent update to server : 10.100.85.59:53 IP Address(es) : 10.105.64.101 The reason the system could not register these RRs was because the DNS server contacted refused the update request.”

    Question 1: Is this summary accurate?

    Question 2: When a client is refused a Dynamic Register by the DNS, what happens other than the Event Log entry above? Will the client be denied Network resources/services, Name Resolutions etc..? Or, will the client simply not be able to refresh its DNS timestamp?

    Thanks for your time.

    Tuesday, June 18, 2019 2:31 PM

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