Specifications
Engineering Guidelines
232
VLAN setting information sources and priorities
The priority levels assigned to each source of VLAN setting information are shown in Table 69.
The highest priority level is 5 and the lowest is 1. When seeking VLAN information the phone
will start with level 5 and proceed through the list in a descending order.
L2 and L3 QoS information sources and priorities
The priority levels assigned to each source used for obtaining L2 and L3 QoS settings are
shown in Table 70. The highest priority level is 5 and the lowest is 1, such that a higher priority
setting always takes precedence over lower attempted re-writes by a lower priority source.
When seeking QoS information the phone will collect information from all available sources
and use the highest priority information available.
The section titled “Potential issues with using LLDP-MED in Cisco environments” on page 233
provides an example of a situation where the initial LAN Policy values are overwritten with
values obtained from a higher priority source.
Note: If a phone has obtained network configuration information via manual
programming, this information will be held by the phone permanently, i.e. other methods
cannot overwrite these values and the values will be maintained even if the phone is
rebooted. This includes the following values:
• IP address for the phone
• default gateway IP address
• subnet mask
• RTC IP address
• TFTP server IP address
• DNS server IP address
• LAN Policy (VLAN, L2 priority, DSCP)
Table 69: Priority levels for the Various Sources of VLAN Setting Information
Source of VLAN
Setting Information
Priority
Level
Notes
Manual Entry (Static) 5 Programmed by installer
LLDP-MED 4 Information obtained from L2 switch
CDP 3 Phones can discover values if CDP is detected on the LAN
DHCP 2 The first time a phone receives DHCP information it must contain an IP
address for the RTC and the TFTP server. This is also true for the double
DHCP fetch mechanism.
If the phone fetches DHCP information a second time, this information will
over write the previous values.
Default Values 1 Default Value = No VLAN, untagged