Did You Know?
Cisco Phone registration pass through well know steps, and to have systematic way of troubleshooting phone registration , first we need to know this List as below
you need to troubleshooting that way , starting from Layer 1 Power , Cabling , Network connectivity , etc
Cisco phone or any other IP Phone should get Power and this will be done using one of two methods
Probably all New phones , will be operating using new IEEE standard , as Cisco way of Powering devices was introduced long time ago.
When phone is connected to switch , switch will send something called FLP “fast link pulse” , the FLP goes to the connected device , the phone or the device has a relay that receive and transmit the signal back to the switch using relay which is built inside the phone , and this mean the device need power
The switch will issue default amount of power and its 6.3 w , in this moment phone will start sending CDP packets using CDP v2 Protocol to negotiate with the switch about needed power
when you have a switch and connect a device , switch will apply approximately 20 Volt DC and will measure current flow , and depending on current flow from connected device , and from that switch will be able to determine what is know as “Power class”
[table id=1 /]
Note : Class 0 usually is used by phones that don’t support IEEE standard
To can check power delivered to each phone , can use show power inline Command as below
issue command on Cisco switch :
DKCOPVEST-F04-USR01#show power inline
Module Available Used Remaining
(Watts) (Watts) (Watts)
------ --------- -------- ---------
1 1440.0 110.3 1329.7
Interface Admin Oper Power Device Class Max
(Watts)
--------- ------ ---------- ------- ------------------- ----- ----
Gi1/0/1 auto on 4.0 Ieee PD 1 30.0
Gi1/0/2 auto on 4.0 Ieee PD 1 30.0
Gi1/0/3 auto off 0.0 n/a n/a 30.0
Gi1/0/4 auto on 4.0 Ieee PD 1 30.0
Gi1/0/5 auto off 0.0 n/a n/a 30.0
Gi1/0/6 auto off 0.0 n/a n/a 30.0
Gi1/0/7 auto off 0.0 n/a n/a 30.0
Gi1/0/8 auto off 0.0 n/a n/a 30.0
Gi1/0/9 auto off 0.0 n/a n/a 30.0
Gi1/0/10 auto off 0.0 n/a n/a 30.0
Gi1/0/11 auto on 10.5 IP Phone 7937 3 30.0
Gi1/0/12 auto on 12.0 IP Phone 7945 3 30.0
Gi1/0/13 auto off 0.0 n/a n/a 30.0
Gi1/0/14 auto off 0.0 n/a n/a 30.0
Gi1/0/15 auto off 0.0 n/a n/a 30.0
Gi1/0/16 auto off 0.0 n/a n/a 30.0
Gi1/0/17 auto off 0.0 n/a n/a 30.0
Gi1/0/18 auto off 0.0 n/a n/a 30.0
Gi1/0/19 auto off 0.0 n/a n/a 30.0
Gi1/0/20 auto off 0.0 n/a n/a 30.0
Gi1/0/21 auto off 0.0 n/a n/a 30.0
Gi1/0/22 auto off 0.0 n/a n/a 30.0
Gi1/0/23 auto off 0.0 n/a n/a 30.0
Gi1/0/24 auto on 10.5 IP Phone 7937 3 30.0
Gi1/0/25 auto off 0.0 n/a n/a 30.0
Gi1/0/26 auto off 0.0 n/a n/a 30.0
Gi1/0/27 auto off 0.0 n/a n/a 30.0
Gi1/0/28 auto off 0.0 n/a n/a 30.0
Gi1/0/29 auto off 0.0 n/a n/a 30.0
Gi1/0/30 auto off 0.0 n/a n/a 30.0
Gi1/0/31 auto off 0.0 n/a n/a 30.0
Gi1/0/32 auto off 0.0 n/a n/a 30.0
Gi1/0/33 auto off 0.0 n/a n/a 30.0
Gi1/0/34 auto off 0.0 n/a n/a 30.0
Gi1/0/35 auto off 0.0 n/a n/a 30.0
Gi1/0/36 auto on 10.5 IP Phone 7937 3 30.0
Gi1/0/37 auto on 12.0 IP Phone 7945 3 30.0
Gi1/0/38 auto off 0.0 n/a n/a 30.0
Gi1/0/39 auto off 0.0 n/a n/a 30.0
Gi1/0/40 auto off 0.0 n/a n/a 30.0
Gi1/0/41 auto off 0.0 n/a n/a 30.0
Gi1/0/42 auto on 12.0 IP Phone 7965 3 30.0
Gi1/0/43 auto on 15.4 AIR-CAP3502I-E-K9 3 30.0
Gi1/0/44 auto on 15.4 AIR-CAP3502I-E-K9 3 30.0
Gi1/0/45 auto off 0.0 n/a n/a 30.0
Gi1/0/46 auto off 0.0 n/a n/a 30.0
Gi1/0/47 auto off 0.0 n/a n/a 30.0
Gi1/0/48 auto off 0.0 n/a n/a 30.0
quick look to the Output , can see below important info
[table id=4 /]
Note : in case switch can’t determine phone power class , will be considered class 0 , as its default class
Phone use CDP to negotiate POE and also to get its Vlan , once phone is powered up will receive instructions from switch to Tag its packets with voice Vlan using 802.1Q protocol
Traffic from PC , will not be tagged , only phone and switch can understand 802.1Q protocol , you can check the Vlan and tagging setting from Interface on switch
switchport mode access
switchport voice vlan 701
spanning-tree portfast
spanning-tree bpduguard enable
!
interface GigabitEthernet1/0/36
description Enterprise User VLAN
switchport access vlan 100
switchport mode access
switchport voice vlan 701
spanning-tree portfast
spanning-tree bpduguard enable
!
DKCOPVEST-F04-USR01#show cdp neighbors gig2/0/28
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
SEP00082FB76036 Gig 2/0/28 167 H P M IP Phone Port 1
after that , phone will initiate DHCP broadcast to request IP address and network setting , you will need to have DHCP server available to provide phone with its network setting, in case you have your DHCP server in same Vlan or same Network subnet “layer 2”, good example for this might be if you have Cisco Voice gateway at remote Branch act as DHCP server , so it should be fine , nothing more is needed
but in case your DHCP is located in a different Network subnet , then Layer 3 device which will receive the DHCP broadcast message from the phone , if that is the case , you will need to redirect this request using IP helper address , to relay the broadcast message to DHCP server
DHCP Commands :
[table id=5 /]
error messages that you might see in dhcp events
for More info , can Check Cisco Tech Notes :
Understanding and Troubleshooting DHCP in Catalyst Switch or Enterprise Networks
phone will receive option 150 as part from Network parameters provided by DHCP server , and Phone is using option 150 to contact TFTP server to download its configuration file.
In case phone couldn’t download its config file , it might be because the phone itself is not added in CUCM configuration , or auto registration is not enabled on the Call manager cluster
If you want to see phone config file when you are opening the switch or router , you can issue command : copy tftp flash
and actually , this is what phone is doing when requesting to download its config file , phone initiate tftp get to download its config file
and if you entered more command , will be able to see entire xml config file for the phone
DKCOPVEST-F04-USR01#copy tftp flash Address or name of remote host []? 10.29.3.140 Source filename []? SEP00082FB76036.cnf.xml Destination filename [SEP00082FB76036.cnf.xml]? Accessing tftp://10.29.3.140/SEP00082FB76036.cnf.xml... Loading SEP00082FB76036.cnf.xml from 10.29.3.140 (via Vlan20): ! [OK - 10167 bytes] 10167 bytes copied in 1.199 secs (8480 bytes/sec) DKCOPVEST-F04-USR01#more SEP00082FB76036.cnf.xml
Cisco UC & Contact Center engineer
Eslam Rizk
