Avaya IP Telephony Konfigurationsanleitung PDF herunterladen (Seite 182)

182 Interoperability

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Assigning VLANs becomes important if you have multiple devices connected to the same switch

port, such as when you use a 3-port-switch to connect a computer and IP phone on the same

network cable. In this case, the system needs to apply the correct VLAN for each device.

Specifying the site-specific options for VLAN

The Business Communications Manager DHCP server resides in default VLAN and is configured

to supply the VLAN information to the IP phones. The DHCP server will supply site-specific

option in the DHCP offer message.

The following definition describes the Nortel IP telephone-specific, Site Specific option. This

option uses the reserved for site specific use DHCP options (DHCP option values 128 to 254) and

must be returned by the DHCP server as part of each DHCP OFFER and ACK message for the IP

telephone to accept these messages as valid. The IP telephone will pull the relevant information

out of this option and use it to configure the IP phone.

Format of field is: Type, Length, Data.

Type (1 octet):

Five choices 0x80, 0x90, 0x9d, 0xbf, 0xfb (128, 144, 157, 191, 251).

Providing a choice of five types allows the IP telephone to work in environments where the

initial choice may already be in use by a different vendor. Pick only one TYPE byte.

Length (1 octet):

(variable depends on the message content)

Data (length octets):

• ASCII based

• format: VLAN-A:XXX,YYY.ZZZ.

where,

VLAN-A: uniquely identifies this as the Nortel DHCP VLAN discovery.

— -A signifies this version of this spec. Future enhancements could use -B, for example.

— ASCII , (comma) is used to separate fields.

— ASCII . (period) is used to signal end of structure.

— XXX, YYY and ZZZ are ASCII-encoded decimal numbers with a range of 0-4095. The

number is used to identify the VLAN Ids. A maximum of 10 VLAN Ids can be

configured. NONE means no VLAN (default VLAN).

The DHCP Offer message carrying VLAN information has no VLAN tag when it is sent out from

the DHCP server. However, a VLAN tag will be added to the packet at the switch port. The packet

will be untagged at the port of the IP phone.

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Avaya IP Telephony Konfigurationsanleitung Seite 182