Yealink SIP-T54S Administrator's Manual page 79

Enter the desired value in the Custom Option(128~254) field.
2.
Click Confirm to accept the change.
3.
DHCP Option 42 and Option 2
Yealink IP phones support using the NTP server address offered by DHCP.
DHCP option 42 is used to specify a list of NTP servers available to the client by IP address. NTP
servers should be listed in order of preference. DHCP option 2 is used to specify the offset of
the client's subnet in seconds from Coordinated Universal Time (UTC).
To update time with the offset time offered by the DHCP server, make sure the DHCP Time
feature is enabled at the web path Settings->Time & Date->DHCP Time. For more
information on how to configure DHCP time feature, refer to
DHCP Option 12 Hostname on the IP Phone
This option specifies the host name of the client. The name may or may not be qualified with
the local domain name (based on
Procedure
DHCP option 12 hostname can be configured using the following methods.
Central Provisioning
(Configuration File)
Web User Interface
Details of Configuration Parameter:
RFC 2132). See RFC 1035
<y0000000000xx>.cfg
Setting Up Your System
NTP Time Server on page 250.
for character restrictions.
Configure the DHCP option 12
hostname.
Parameter:
static.network.dhcp_host_name
Configure the DHCP option 12
hostname.
Navigate to:
http://<phoneIPAddress>/servlet?p=
features-general&q=load
53