• The DHCP request contains standard IP Deskphone IP DHCP option requests from the
point when the IP Deskphone does not receive the VLAN information. These options
include the Vendor Specific and all Site Specific options.
2. The DHCP server receives the request. If the server is configured, the DHCP server returns
a DHCP Offer message with a special text string in the Vendor Specific option or one of the
Site Specific options.
The following is the format of the text in the option:
VLAN-A:XXX+YYY+ZZZ+…
where VLAN-A is a substring followed with VLAN information. XXX, YYY, ZZZ are the
numbers of the supported VLANs. There can be from 1 to 10 different VLANs. Each VLAN is
separated with a symbol +.
3. After receiving the DHCP Offer message, the IP Deskphone scans each Vendor and Site
Specific option for the VLAN-A string.
4. If the IP Deskphone finds the VLAN-A string, it tries each VLAN and in turn XXX, YYY, ZZZ
searches for a DHCP server.
5. The search is done by sending a DHCP Discover message looking for a DHCP Offer
message as a response.
6. If the IP Deskphone finds a response, it discontinues its DHCP exchange on the untagged
channel and continues its DHCP exchange on the “discovered” VLAN.
7. If there is no response, the initial untagged Discover message assumes there is no VLAN
configuration information available from the DHCP server and continues using untagged
packets. When the IP Deskphone sends its first DHCP Discover message, it does not know
if it can find VLAN configuration information. If it does discover VLAN information, it
continues the VLAN configuration as described above. If it does not find any VLAN
information, it assumes there is only a Configuration Phase.
DHCP options
The DHCP protocol provides options mechanisms for the client and server to exchange information
in addition to the standard Bootstrap Protocol (BOOTP) information. This section describes the
client and server options supported by the IP Deskphone.
•
IP Deskphone to Server options on page 103
• Server to IP Deskphone options on page 104
IP Deskphone to Server options
When a DHCP client sends DHCP Discover and Request messages, it includes a list of options as
part of the request. The IP Deskphone DHCP client sends the following options:
DHCP options
March 2015 SIP Software for Avaya 1200 Series IP Deskphones-Administration 103
Comments? infodev@avaya.com
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