Information Technology Reference
In-Depth Information
TFTP problems
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CUCM registration problems
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Let's examine a scenario in which the phone is not registering. In this scenario, the phones
are supposed to use DHCP. Each point that follows describes a possible place where prob-
lems may be happening. Best practices dictate that we follow these troubleshooting pro-
cedures in the order that follows; there will be times when experience or specific
knowledge allows us to skip to a later procedure:
Local to the IP Phone:
The IP Phone itself can display its current configuration and
settings, which can quickly indicate which part of the sequence has failed. Press the
Settings
button, and then select Network Configuration from the displayed list.
Scroll down to
IP Configuration
and verify that the phone has received an IP address
(in the correct subnet), subnet mask, default gateway, and the correct TFTP server ad-
dress. If the entries are absent or incorrect, verify that the phone is configured to use
DHCP by pressing
Settings > Network Configuration
, and then scrolling down to
DHCP Enabled
and verifying that it is set to
Ye s
. If all that is correct, but the phone is
still not receiving an address from DHCP, move on to the next step.
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VLAN or switch mismatches:
Verify that the switch is correctly configured to sup-
port IP Phones. The switch should have a voice VLAN defined, and if there is a PC
connected to the phone, a separate access VLAN. (See Chapter 3, “Understanding the
Cisco IP Phone Concepts and Registration,” for the configurations.) Verify that the
VLAN numbers are correct. If the switch configuration is correct, move on.
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DHCP problems:
Verify that the DHCP server is running and that it has not run out
of IP addresses. Make sure that the DHCP scopes (subnets or pools) are correct with
respect to the IP address range being assigned, the subnet mask, default gateway, and
Option 150 (TFTP server IP address). On the IP Phone, navigate to
Settings
>
Network Configuration
. Verify that the
DHCP Server
entry lists the IP address of
the correct DHCP server. Check that an IP address has been assigned, and if so, that it
is in the correct range. Verify that the
TFTP Server 1
address entry is correct.
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Note:
IftheDHCPserverisonaremotesubnetfromtheIPphones,thelocalrouter
blocks the DHCP broadcasts by default. Use the
ip helper-address <ip_address>
command
on the local router to allow it to forward DHCP requests to the IP of the DHCP server.
TFTP problems:
As it boots up, the phone queries the TFTP server (at the address
learned via DHCP) for its configuration file. The filename it asks for is called
SEP<mac>.cnf.xml. If the phone has been successfully added to the CUCM or Cisco
Unified Communication Manager Express (CME) application, the file will exist and
will be downloaded to the phone. If the phone has never been added to the application
before, the file will not be there. The phone will then ask for the file called XMLDe-
fault.cnf.xml. This default file is always available. If the phone is not getting its config
file, verify that the phone has the correct TFTP address in the
Network Configuration
list. Verify that the TFTP service is running on the server at that IP. You can check on
the status of the TFTP process on the phone by pressing Settings > Status Messages;
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