Yealink SIP-T2XP Administrator's Manual page 387

The IP phone will always use the results returned from the static DNS cache.

IP phones can be configured to use static DNS cache preferentially. Static DNS cache is
configurable on a per-line basis.
Procedure
Static DNS cache can be configured only using the configuration files.
Configuration File
Configure NAPTR/SRV/A records.
Parameters:
dns_cache_naptr.X.name
dns_cache_naptr.X.flags
dns_cache_naptr.X.order
dns_cache_naptr.X.preference
dns_cache_naptr.X.replace
dns_cache_naptr.X.service
dns_cache_naptr.X.ttl
<y0000000000
xx>.cfg
dns_cache_srv.X.name
dns_cache_srv.X.port
dns_cache_srv.X.priority
dns_cache_srv.X.target
dns_cache_srv.X.weight
dns_cache_srv.X.ttl
dns_cache_a.X.name
dns_cache_a.X.ip
dns_cache_a.X.ttl
Configure the IP phone whether to cache
the additional DNS records.
Parameter:
account.X.dns_cache_type
<MAC>.cfg
Configure the IP phone whether to use
static DNS cache preferentially.
Parameter:
account.X.static_cache_pri
Configuring Advanced Features
369