DDNS conflict resolution - BlueCat Address Manager - 9.1.0

Address Manager Administration Guide

prodname
BlueCat Address Manager
version_custom
9.1.0

The following section outlines example scenarios where DDNS conflicts might occur and possible configurations to resolve these conflicts.

Dual-stack environments

When a DHCP server is configured to distribute IPv4 and IPv6 leases, DDNS conflicts can occur when a host that is using the same hostname for both IPv4 and IPv6 networks receives an IPv4 address and attempts to receive an IPv6 address, or vice versa. The host fails to receive the other IP address type, as a "guard" record exists for that host record. To resolve the issue, you must configure the following DHCP Service Options:
  • Update Conflict Detection—when the DHCP server performs a DDNS update for a client, an additional "guard" (either TXT or DHCID) record is added to DNS to record the ID of the client that owns the DNS entry. This must be added as a DHCP Service Option and set to Enabled.
    Attention: You must only configure the Update Conflict Detection Service option at the configuration and server levels.
  • DDNS Dual Stack Mixed Mode—enables Dual-Stack Mixed Mode rules to be used for DDNS conflict resolution. This must be added as a DHCPv4 and DHCPv6 Service Option and set to Enabled.
  • DDNS Update Style—defines the DDNS update style when a DHCP server performs a DDNS update for a client. The update style can be either standard or interim. DHCP servers using standard update style create DHCID "guard" records and servers using interim update style create TXT "guard" records. This must be configured as a DHCPv4 and DHCPv6 Service Option. However, DHCPv4 and DHCPv6 must be configured to use different DDNS update styles.
  • DDNS Other Guard Is Dynamic—defines whether the presence of a DHCID "guard" record that was produced using a different DDNS update style allows a DNS entry to be overwritten. This must be added as a DHCPv4 and DHCPv6 Service Option and set to Enabled.

Hosts roaming between networks

When a DHCP server is servicing IP addresses to multiple networks or subnets and hosts move between wired and wireless networks, the DNS host record may not be updated as an existing "guard" record exists for that host for an IP address on a different subnet. To resolve the issue, you must configure the following DHCP Service Options:
  • Update Conflict Detection—when the DHCP server performs a DDNS update for a client, an additional "guard" (either TXT or DHCID) record is added to DNS to record the ID of the client that owns the DNS entry. This must be added as a DHCP Service Option and set to Enabled.
    Attention: You must only configure the Update Conflict Detection Service option at the configuration and server levels.
  • DDNS Dual Stack Mixed Mode—enables Dual-Stack Mixed Mode rules to be used for DDNS conflict resolution. This must be added as a DHCP Service Option and set to Enabled.
  • DDNS Guard ID Must Match—defines whether a client ID within a DHCID resource record must match the client ID of a DNS update to permit DNS entries associated to that DHCID record to be overwritten. This must be added as a DHCP Service Option and set to Disabled.
Note: If you are resolving hosts roaming between networks in a dual-stack environment, you must configure the DDNS Other Guard Is Dynamic DHCP Service option and set the value to Enabled.