AM; Reviewed:
WCH 3/18/2004
Solution & Interoperability Test Lab Application Notes
© 2004 Avaya Inc. All Rights Reserved.
3 of 10
Linux-DHCP.doc
The following DHCP server parameters were configured for the endpoints on the native data
VLAN:
• Data endpoints IP address Range (178.16.13.100 – 178.16.13.250)
• Router IP address (178.16.13.1)
• Subnet broadcast IP address (178.16.13.255)
• Subnet Mask (255.255.255.0)
• L2Q=1 - IEEE 802.1Q trunking
• L2QVLAN=120 - Voice VLAN
The following DHCP server parameters were configured for the Avaya 4600 Series IP
Telephones on the voice VLAN:
• Telephone IP address Range (178.16.12.100 – 178.16.12.250)
• Router IP address (178.16.12.1)
• Subnet broadcast IP address (178.16.12.255)
• Subnet Mask (255.255.255.0)
• IP address of C-LAN board – MCIPADD (178.16.12.21)
• Gatekeeper port - MCPORT (Default: 1719)
• TFTP server IP address – TFTPSRVR (178.16.12.100)
The following occurs when an IP telephone is installed (or reset). The IP telephone will initially
send an untagged DHCP request. The Avaya P333R switch port is configured with both an
untagged VLAN and tagged VLAN for the port. The untagged DHCP request will be associated
with the untagged VLAN on the port. The Avaya P333R router interface on that VLAN has IP
address 178.16.13.1. When the router interface relays the DHCP request to the configured
DHCP server (178.16.13.66), it will use 178.16.13.1 as the source address. The DHCP server
associates this request with the 178.16.13.0 scope and returns a reply with Option 176 string set,
instructing the requestor to enable 802.1Q tagging with voice VLAN ID 120. The IP telephone
receiving this reply will release the supplied IP address and issue a new DHCP request with
VLAN ID 120. This request will be associated with the tagged VLAN on the port. The Avaya
P333R interface of this VLAN has IP address 178.16.12.1 and will relay the DHCP request to
the DHCP server with this address as the source. The DHCP server associates this address with
scope 178.16.12.0 and replies with an IP address from that scope as well as several parameters in
the Option 176 string.
Computers attached to the Avaya IP telephones issue untagged DHCP requests. These requests
will be serviced the same as the initial request from the phone. However, the computer will
ignore the Option 176 values specifying a new VLAN. Therefore, no new DHCP request is
issued.
Note: The Avaya P333R switch and TFTP server configurations are out of the scope of this
document. Please consult the appropriate user guides for more information on how to configure
these devices.