Configuring VoIP: Basic level_Packet Tracer

Posted: June 10, 2013 in Networking
Tags: ,


On this article I will describe superficially about the basic concepts that you must have in order to have the…….basic info and complete this LAB successfully . 🙂

So, Gents and Ladys…

Lest start describing what is VoIP: as the name says, VoIP is Voice over IP. Anything that allows you to communicate, I mean, to transmit your voice over the IP, or the Internet , is VoIP.

There are distinct vendors of VoIP,  however, on this tutorial, we will focus on Cisco, we will focus on the following product: Cisco Unified Call Manager Express (commonly known as CUCME)

There are Routers called ISR: Integrated Service Routers, which come with certain services and features inside it.

CUCME is one example of these features and services that are build-in the router (or are router-based).

There is a technology called PoE: Power Over Ethernet, which allows equipment to send data and power at the same time to certain devices that are PoE compatible.

So, knowing these few things, lets get to work.

Lets mount the following topology:










Pay attention that on Packet Tracer the PoE technology isn’t implemented yet. 🙂

This is why, to power on the IP Phones we will connect a power adapter to it.

As the Switch is not PoE.

See how to connect the power adapter to the IP Phone on the picture below:












So the first thing to be done is to configure the IP address of the router:

Router#configure terminal
Router(config)#interface FastEthernet0/0
Router(config-if)#ip address
Router(config-if)#no shutdown

A DHCP server is used to assign IP addresses to the IP Phones.

A TFTP server is used to allow the phones to get the firmware and certain configurations files from the router, this is done by the option 150 of the DHCP.

1. Router(config)#ip dhcp pool VOICE
2. Router(dhcp-config)#network
3. Router(dhcp-config)#default-router
4. Router(dhcp-config)#option 150 ip

CLI description:

1. Giving a name to the DHCP pool, in this case, this pool is for the phones only,

2. The network that is covered by the DHCP

3. The default router for this IP distribution

4. Configuration of the TFTP

Next step to do is to configure the Call Manager Express itself on the router,

1. Router(config)#telephony-service
2. Router(config-telephony)#max-dn 5
3. Router(config-telephony)#max-ephones 5
4. Router(config-telephony)#ip source-address port 2000
5. Router(config-telephony)#auto assign 1 to 5

CLI descrition:

1. Enters to the telephony services

2. max number of phone lines

3. max number of telephones

4. The IP of the router where the telephones will be registered and the source address where is running the DHCP and TFTP services, which will be the router itself. And the port used for the phones, the default one is 2000 (for SCCP phones)

5. is to automatically register the phones, on this case is from phone 1 to 5 (you can register the IP Phones yourself, next time I will show how to do it)

Next step is to configure the Switch, on this case, there is not too much to do, just configure a VLAN for voice traffic. We must add this VLAN to separate the data traffic from the Voice traffic. Data will be sent to the computers and voice traffic will be sent to the IP Phones.

As we configured 5 max IP Phones, so we will configure 5 interfaces of the switch to the Voice VLAN.

As you can see on the image below,







P.S.: The first interface of the switch on my scenario, is connected to my router, so we will exclude it on this VLAN configuration.

Switch(config)#int range fastEthernet 0/2-6
Switch(config-if-range)#switchport mode access
Switch(config-if-range)#switchport voice vlan 1

Despite being on the same VLAN  (data and voice), virtually the traffic will be separated. (If you wish, you can create another VLAN for the VOICE traffic)

Now is time to give numbers to the lines that will be used on the IP Phones:

P.S: We have configured 5 max IP Phones, so we will configure 5 max numbers for the lines.

Router(config)#ephone-dn 1
Router(config-ephone-dn)#number 10

Router(config)#ephone-dn 2
Router(config-ephone-dn)#number 20

Router(config)#ephone-dn 3
Router(config-ephone-dn)#number 30

Router(config)#ephone-dn 4
Router(config-ephone-dn)#number 40

Router(config)#ephone-dn 5
Router(config-ephone-dn)#number 50

Its almost there, the only confirmation we need is that the IP Phones were successfully registered on the CUCME (This process can take a while).
Hover the mouse on the IP Phone to see if it successfully received the IP address and the phone number (If not, wait a little bit more. P.S.: This process can take a while).


Once you have the confirmation, you can add the remaining 4 IP Phones on the switch, remembering that these IP Phones must be added on the same interfaces were have configured the Voice VLAN. 🙂










Make a call to test the configurations

1. Look at the pictures below:










2. Dial from one phone to another, on this case we will dial from IP Phone number 10 to IP Phone number 20 (to dial, just mark the number and click on the earphone)









To pick up the call on the other phone, just click on the earphone too and…VOILA

Hope you finish sucessfully the configurations.

Any doubts, you can post here your comments so that anyone can see it or you can send me an email:

See you next time…. 🙂


Cisco Learning Network Store

Best regards,

Edson Vuma


  1. Wonderful article! We are linking to this great post on our site.

    Keep up the good writing.


  2. I don’t even know how I finished up here, however I thought this submit
    wass great. I don’t recognise who you are but certainly you’re going to a famous blogger for those who aren’t already.


  3. moe hamad says:

    i cant find telephony-service in my router (packet tracer) it gives me Invalid input error message

    Liked by 1 person

  4. Malik says:

    when i enter (option 150 ip it tells me invalid input

    Liked by 1 person

  5. KARZAN says:

    Hi edson could you send vce 1.1.7 for ccnp 642-902 route coz mine it will give me stream read error so can you guide me for that or send it to my email dress as winrar

    Liked by 1 person

  6. mutaz says:

    just i can say thanks man
    very thanks


  7. Luke says:


    Your configuration is quite comprehensive but I am having some troubles with the telephony service as I get an error msg when i try to switch to telephony-service. I am using pt 6.1.1.
    could you help me pls??

    Liked by 1 person

  8. Carl Jason N. Santiago says:

    Hi can you please help me.


  9. Lumumba Hasan says:

    I want to say thank you this has been the best one that I have found that works. I have one question. I get this when I have the phone powered on: %DHCPD-4-PING_CONFLICT: DHCP address conflict: server pinged It keeps repeating the same message until I turn off the phone. Once its off and entered all commands then turn the phones on last they get their IP and work.


    • Edson Vuma says:

      Hi, Lumumba Hasan

      Thanks for your time reading my articles and thanks for the feedback.
      Kindly, can you send me the .PKT file so that I can give a deep look at what might be causing this “issue”?

      Warm regards,


  10. kins says:

    can you do it with two routers? 1 ip phone for 1 router and 1 to other router and connect it. thanks in advance 🙂


  11. Adnan Askari says:

    wonderful man !


  12. MaAs says:

    It worked like a charm buddy, thanks!


  13. sengphearin says:

    Hi Edson,

    Thank you for your tutorial, but could you please help to elaborate more about auto assign 1 to 5 command ? what does it function? sometimes i saw people used assign 4 to 6.



    • Edson Vuma says:

      Hi Phearin,

      Thanks for your feedback.

      Regarding the AUTO ASSIGN command, it does what it says which is auto assignment of DN’s to the Ephones.
      So, when we say:
      auto assign 1 to 5
      We are telling the CME Router to auto assign from DN tag 1 to DN tag 5.
      In summary, the first value is the starting DN tag and the second value is the stop DN tag.

      When people use auto assign 4 to 6 what it means then??
      Exactly what u though, it means that they are telling the CME Router to auto assign DN tag 4, 5 and 6 to the ephones.

      Hope I have clarified your question.

      Warm regards,
      Edson Vuma


  14. alexmunoz905 says:

    Thank you so much for this! I once set up one phone on a router in real life, but the other phones were acting weird. This worked in packet tracer and it made me happy. Thank you man!


    • Edson Vuma says:

      Hi Alex

      Thank you so much for the feedback.
      I’m very happy you made it.
      Keep the spirit and check my other articles about Dial Peers and CUCM related.

      And….dont forget to share it.

      Warm regards
      Edson Vuma


  15. shah says:

    can we use new model of router cisco router 2901 or 2911 which is use gigabit technology ? im using packet tracer 7.0


  16. Engels says:

    Hi, thanks for this easy to follow article. I’m a newbie and got lost when setting separating into 2 vlans, one for data and other for voice using the 2960 SW on Packet Tracer with the 2811 router. Used trunk on the fa 0/1 to the router, the phones wont work… any hint? Thanks


  17. Engels says:

    Thanks for your reply Edson. I was able to find another PT example. I had to use sub interfaces on the router interface facing the trunk port on the L2 switch, that is what’s called router-on-a-stick, now the phones work fine, so it was a misconfiguration on my part. I know some prefer to use a L3 switch, but it was nice to try vlans separation on a L2 one . Regards!!!

    Liked by 1 person

  18. grey says:

    still very helpful


  19. transex says:

    Everything is very open with a really clear description of the issues.
    It was definitely informative. Your site is extremely helpful.
    Many thanks for sharing!


  20. khemis peter says:

    i like steps good teacher it works out well


  21. travestis rj says:

    Thanks for another informative blog. The place else may just I am
    getting that kind of information written in such an ideal approach?

    I have a project that I’m just now working on, and I have been at the glance out for such info.


  22. Brian says:

    Thanks so much for sharing! Excellent lab for beginners…as it was clear and concise!!


  23. mustafa al jaber says:

    Hi Edson,

    how many Maximum phone line in router 2811 ???? i am try to buy one used


    • Edson Vuma says:

      Hi Mustafa

      The max-dn command limits the number of extensions (ephone-dns) available in a Cisco Unified CME system. The maximum number of ephone-dns that you can create depends on the software version, router platform, and amount of memory that you have installed. Type ? to display range.

      Warm regards,
      Edson Vuma


  24. mark says:

    hello sir,
    i have two Vlans on a switch with 2 phones. Each phone is connected to a different vlan,
    i have a router that have 2 subinterfaces for each vlan 10/20 both are for vlan …
    my main problem is that my phones wont get the line number for some reasons that i dont know :\
    i tried ephone-dn 1 … number 5555 after that i did telephony-service and etc my phone wont get that 5555 number …
    thanks in advanced.


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