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's 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. Add this as a DHCP Service option 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. Add this as a DHCPv4 and DHCPv6 Service option 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. Add this as a DHCPv4 and DHCPv6 Service option. However, you must configure DHCPv4 and DHCPv6 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. Add this as a DHCPv4 and DHCPv6 Service option 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. Add this as a DHCP Service option 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. Add this as a DHCP Service option 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. Add this as a DHCP Service option 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.