An ephone-dn can be described in its simplest form as a directory number which can be assigned to one or more buttons on one or more Cisco IP phones.  We can configure each ephone-dns either as single or dual mode ephone-dn.  We will learn about the difference between the two in the subsequent sections.

Single line ephone-dn – Only one call can occur from this type of e-phone-dn.  It is able to make or receive only one call at a time.  If a call arrives on an ephone-dn where a call is already active, the caller will get a busy signal.  It does not support call waiting and is mostly used for paging, intercom, call parking, and MOH feeds.  It is also used to create a virtual voice port.

Dual-line ephone-dn – This ephone type supports two call connections at the same time, as it can handle two calls simultaneously. Since it has two channels, it could have one number or two (– Dual-number ephone-dn – primary and secondary), this type of ephone has features such as call waiting, call transfer and conferencing.  Dual-line should not be used for call waiting, call transfer or conferencing.

One more type of ephone-dn supported by cisco unified CME is a shared ephone-dn.

Shared ephone-dn – Here, the ephone appears on 2/more different phones, but using the same ephone-dn and number.  All the ephones configured with these ephone-dn will ring when a call arrives at the ephone-dn and when a call is placed on hold any phone can retrieve it.

Other ephone-dn supported by Cisco Unified CME is multiple ephone-dns on one ephone,  multiple ephone-dns on Different ephones and Overlay ephone-dn.

In most environments you will see dual line configurations are used.  Single line configurations are generally used for functions such as intercom and paging.  Now we will look at how to configure the ephone-dn.

CME_Voice# config t

Enter configuration commands, one per line, end with Ctrl/Z

CME_Voice (Config) #ephone-dn?

ephone-dn tag

CME_Voice (config) # ephone-dn 1

CME_Voice (config-ephone-dn) # number?

WORD A sequence of digits – representing telephone number

CME_Voice (config-ephone-dn) #number 1000

CME_Voice (config-ephone-dn) # exit

CME_Voice (config-ephone-dn) # ephone-dn 2?

Dual-line dual line DN (2 calls per line/button)

CME_Voice (config) # ephone-dn 2 dual-line

CME_Voice (config-ephone-dn) # number 1001

The tag is a logical number used while assigning the ephone-dn to an ephone.  We can choose any ephone-dn tag from the range while creating the ephone-dn as long as the total numbers of ephone-dn don’t exceed the number mentioned in max-dn command.

Creating  a greater number of ephone-dns than the maximum specified will lead to an error stating dn tag exceeds legal range 1 to max-dn .

The number parameter syntax which is used to assign a directory number to an ephone-dn also supports a secondary number value. For example we can enter:

CME_Voice (config) # ephone-dn 2 dual-line

CME_Voice (config-ephone-dn) # number 1001 secondary 4805551001

This statement permits use of ephone-dn for multiple numbers.  This is useful particularly in a scenario where we wanted an internal extension to be reached if someone on the internal network dialed a four digit extension or the full PSTN direct inward dial number.

When an ephone is configured in CME, the configuration is directly applied to a single Cisco IP phone or softphone managed by the CME router. Use the following syntax to create an ephone:

CME_Voice (config) # ephone?

Ethernet phone tag

CME_Voice (config) # ephone 1

CME_Voice (config-ephone) #

Once we enter command ephone the CME router takes you into ephone configuration mode. Each command entered impacts the IP phone matched to this ephone.

After creating an ephone we can logically link it to the physical IP phone it corresponds to.  The MAC address of IP phone is used by CME for this purpose.  There are three ways which are used to detect MAC address of IP phone by CME.

On the box of the Cisco IP phone – the box Cisco IP phone ships in has MAC address of phone number.

On the back of Cisco IP phone – the back of IP phone has MAC address label attached.

From the settings menu of the cisco IP phone – Choosing settings and network configuration on IP phone displays the MAC address of IP phone on display panel.

Once we have MAC address of IP phone we can enter it from ephone configuration mode using the following syntax:

CME_Voice (config) # ephone 1

CME_Voice (config-ephone) # mac-address?

H.H.H MAC address

CME_Voice (config-ephone) # mac-address 0014.1c48.e71a

Use show ephone command to verify the IP phone registration status.

CME_Voice# Show ephone

Ephone-1 MAC: 0014.1c48.E6D1 TCP socket:

[2] activeline: 0 REGISTERED in SCCP ver 11 and server in ver 8

mediaActive:0 offhook:0 ringing :0 reset:0 reset_sent:0 paging 0 debug:0 caps:8

IP: 52777 Telecaster 7960 keepalive 0 max_line 6


Once the ephone is linked with the physical phone we can start assigning buttons to the ephone-dns.

To link the ephone and the ephone-dns we can use following command:


CME_Voice (config) # ephone 1

CME_Voice (config-ephone) # button 1:2

CME_Voice (config-ephone) # restart

The button 1:2 assigns ephone-dn 2 to button 1 of ephone 1. The colon is a separator which indicates it is a normal ring button assignment.

We can also assign multiple lines to a phone by either entering multiple button commands or putting multiple entries on the same line as show below:

CME_Voice (config) # ephone 1

CME_Voice (config-ephone) # button 1:2

CME_Voice (config-ephone) # button 2:1

Assign using a single command line.

CME_Voice (config) # ephone 1

CME_Voice (config-ephone) # button 1:2 2:1

Use show ephone command to verify button assignment.

There are some other separators which are used in button command apart from: (colon) as shown in table 1 below:

Table 1: Separators to be Used with Button Command

Separator character



Normal ring


Call waiting beep


Feature ring


Monitor mode


Overlay line


Overlay line with call waiting


Overlay expansion/rollover


Silent ring


Watch mode


This concludes our CCNA Voice exam lesson on understanding different types of ephones and ephone-dns, and how they are configured and used along with what features are supported by them.