Cisco E20 - What Happens Next

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Cisco IP Video Phone E20 Administrator guide
D143 30.12 Administrator guide Cisco IP Video Phone E20, TE4.1 November 2011.
All contents are Copyright © 2010–2011, Cisco Systems, Inc. All rights reserved.
What Happens Next
Once a provisioning mode has been chosen by the user
(or the xConguration Network 1 VLAN Voice
Mode and xConguration Network 1 VLAN Data
Mode parameters have been manually congured), and
the E20 has decided which VLAN it belongs on, the fol-
lowing sequence of events occur:
1. The E20 will broadcast a DHCP DISCOVER on the
VLAN to which it assigned. The DHCP server is
expected to provide all the ordinary parameters—IP
address, subnet mask, default router, domain name,
DNS server(s), NTP server(s). In addition, it may pro-
vide one or more vendor-specic options to point the
E20 to its provisioning server:
a. Option 42, containing specic vendor-encapsulated-
options containing either of the following two methods:
i. PROVISIONINGSERVER and
PROVISIONINGDOMAIN
ii. TMSSERVER
b. Option 242, containing a 32-bit dotted-decimal
notation IP address of the Cisco Telepresence Man-
agement Suite (TMS).
c. Option 150, containing a 32-bit dotted-decimal
notation IP address of the Cisco Unied Communi-
cations Manager (UC Manager).
d. Option 66, containing a 32-bit dotted-decimal
notation IP address of a TFTP server.
2. The E20 then proceeds to obtain its conguration in
the following sequence.
a. Do a DNS lookup for tandbergprovisioning.<your_
domain_name>. If successful, attempt to use HTTP
to fetch the conguration from that server.
b. If DHCP option 42 was received and contains the
PROVISIONINGSERVER and PROVISIONINGDO-
MAIN parameters, attempt to use VCS mode SIP-
based provisioning.
c. If DHCP option 42 was received and contains the
TMSSERVER parameter, attempt to use TMS mode
HTTP-based provisioning.
d. If DHCP option 150 was received, containing the
IP address of the Unied Communications Manager
provisioning server, attempt to contact that server
using CUCM mode HTTP-based provisioning.
e. If DHCP option 66 was received, containing the IP
address of a TFTP server, attempt to contact that
server using TFTP.
f. Do a DNS lookup for provisioning.tandberg.com. If
successful, attempt to use HTTP to fetch the con-
guration from that server.
Note: The DHCP process is actually done in the back-
ground prior to the Startup Wizard being displayed. This
means that during the rst-time bootup, or after a factory
reset has been done, the E20 will initially obtain a DHCP
lease in the native VLAN. If CUCM mode is then chosen,
and CDP indicates that a VLAN should be used, the E20
will release the address it received in the native VLAN,
restart its IP stack, and re-DHCP a new address in the
auxiliary VLAN. This may result in temporary usage of IP
addresses in the native VLAN during the rst-time bootup.
A Note about DHCP Option 150
Some customers congure their DHCP server to process
DHCP requests based on attributes contained within the
request. For example, at Cisco, if a device requests DHCP
Option 150 in its DHCP DISCOVER, the DHCP server
will attempt to assign an address from a correspond-
ing Auxiliary (Voice) VLAN. If the DHCP DISCOVER was
sourced from a data VLAN, the DHCP server will fail to
issue a DHCP OFFER for that device. This means that an
E20 on Cisco’s internal network, if set to use VCS (and
hence the xConguration Network 1 VLAN Voice
Mode and xConguration Network 1 VLAN Data
Mode parameters are set to Off), the E20 will not be
issued an IP address, because the Cisco DHCP server
will not OFFER an address to a device on the data VLAN
which has requested DHCP Option 150 in its DISCOVER.
The workaround for Cisco internal users who are using
the E20 in VCS mode is to manually set the xCongura-
tion Network 1 VLA N Voice Mode and xCongu-
ration Network 1 VLAN Data Mode parameters to
Auto. Other customers may have similar DHCP rules in
place, so the user should consult their DHCP administrator
to determine which VLAN they should set their E20 to use,
and set the xConguration Network 1 VLAN Voice
Mode and xConguration Network 1 VLAN Data
Mode parameters accordingly.
Summary
This document has briey introduced the history and
benets of the Cisco Discovery Protocol (CDP) and its
behavior on the Cisco E20 IP Video Phone release TE4.0.
CDP is a powerful mechanism for automating the ap-
plication of VLANs and Quality of Service for voice/video
devices, and existing TANDBERG customers are strongly
encouraged to begin exploring its benets and preparing
their networks so that they can begin leveraging VLANs,
AutoQoS and VLAN-based security policies for the
former-TANDBERG endpoints.