User's Manual

ManualsBrandsAvaya ManualsIP DeskphonesAvaya Communication Server 1000 IP Phones Fundamentals

441

442

443

444

445

446

447

448

449

450

442 Features

For example, the IP Phone 2004 responds only to DHCPOFFERs that

have the same unique string identifier, "Nortel-i2004-A", as the IP Phone

2004. This string must appear in the beginning of the list of Voice Gateway

Media Card parameters. Without this string, the IP Phone 2004 does not

accept the DHPCOFFER, even if all parameters requested and Voice

Gateway Media Card information are present. If no valid DHCPOFFERs

are sent then, the IP Phone 2004 keeps broadcasting in search of a valid

offer.

With multiple DHCP servers on the same network, a problem can occur

if any two of the servers have overlapping IP address range and no

redundancy. DHCP redundancy is a property of DHCP servers. This

redundancy enables different DHCP servers to serve the same IP address

ranges simultaneously. Administrators must be aware that not all DHCP

servers have this capability.

IP Phone support for DHCP

This section covers the three uses of DHCP (Full, Partial, and VLAN Auto

Discovery).

An "IP Phone 2004-aware" DHCP server is needed only for the Full DHCP

and VLAN Auto discovery. An IP Phone can obtain its IP address and

subnet mask using Partial DHCP. The "IP Phone 2004 aware" part returns

the Node IP and registration port number. In the case of the DHCP Auto

Discovery, it returns the VLAN IDs. Separate DHCP vendor-specific

entries are needed for the Full DHCP data and the VLAN Auto Discovery

data. When using the VLAN Auto Discovery, both Full DHCP and VLAN

Auto Discovery must be configured. Full DHCP and Auto VLAN are

implemented as separate functions in the IP Phone firmware. However, in

practice, Full DHCP and Auto VLAN are frequently used together.

DHCP support in the IP Phone requires sending a "Class Identifier"

option with the value "Nortel-i2004-A" in each DHCP DHCPOFFER and

DHCPACK message. Additionally, the telephone checks for either a

Vendor Specific option message with a specific, unique to Nortel IP Phone

2004, encapsulated sub-type, or a Site Specific DHCP option.

In either case, an IP Phone 2004-specific option must be returned by the

IP Phone 2004 aware DHCP server in all Offer and Acknowledgement

(ACK) messages. The IP Phone uses this option’s data it to configure the

information required to connect to the TPS.

The DHCP response is parsed to extract the IP Phone’s IP address,

subnet mask, and gateway IP address. The vendor specific field is then

parsed to extract the Server 1 (minimum) and optionally Server 2. By

default, Server 1 is always assumed to be the "primary" server after a

DHCP session.

Nortel Communication Server 1000

IP Phones Fundamentals

NN43001-368 05.06 30 April 2010