5 THE VOIP TECHNOLOGY

5.1 Introduction to the VoIP Technology

VoIP (Voice over Internet Protocol) technology is a technique for transmitting speech over data communication links using the IP protocol (packet switching). The main advantages of VoIP over traditional telephony are:

 low cost of cabling (a working IP network is sufficient),

 free calls on the internal network,

 integration with services such as data or video transmission.

The main disadvantages VoIP over traditional telephony are:

 greater unreliability of services,

 need for dedicated hardware and software,

 communications are more exposed to the possibility of eavesdropping.

5.2 IP Phone End Device

An IP phone (IP Phone) is a terminal device with the ability to communicate via voice and the existing IP network. Therefore, the IP Phone has an Ethernet port marked Switch. In addition, it must be connected to a power supply.

There is only one model of IP Phone available in Packet Tracer, namely the 7960. In order to start building a telephone network, we must first insert the phone into the program's main board.

Figure 5.1 Choice of IP phone model 7960

In the bottom left corner of the program, find the "End Devices" device group, click on it and then select "IP Phone" and move the device to the board. The IP Phone will be represented as the following icon:

Figure 5.2 IP phone model 7960

Before we move on to describing how to prepare the phone for operation, it is worthwhile for us to be able to simulate the dialing and busy tones.

To enable this, go to the Packet Tracer main menu and select Options  Preferences, then under "Interface" select "Play Telephony Sound".

Figure 5.3 Option Play Telephony Sound

Now we can move on to the section describing how to prepare the IP phone for operation.

5.3 Preparing the IP Telephone for Operation The IP Phone must be connected to an external voltage source. To do this, click on the IP Phone. A window appears with the Physical tab, where you use the mouse to connect (drag) the power supply (VoIP power adapter) to the socket indicated by the arrow in the figure.

Figure 5.4 Connecting power to an IP phone.

Figure 5.5 Appearance of the bottom part of the IP phone after connecting the power supply

In the "Config" tab, we can change the Display Name for the telephone.

Figure 5.6 Changing the IP phone name

The "GUI" tab contains the view of the IP telephone (handset, display panel and keypad). We will use this tab only after configuring the IP network, telephone numbers and when testing connectivity.

Figure 5.7 View of the IP phone on the GUI tab

To run a simple IP-based telephone network, you need a minimum of one router, one switch and two IP phones.

However, not every router has the necessary software to become a telephone exchange. In Packet Tracer, the 2811 meets this requirement. The VoIP PBX management software for Cisco routers is called Call Manager Express.

5.4 Call Manager Express

Call Manager Express (CME) software runs on Cisco routers and acts as a virtual PBX for IP telephony. For the description of Voice over IP technology in this chapter, the 2811 was chosen because in Packet Tracer only this model supports IP telephony.

5.5 Configuring a Simple VoIP Network

In order to set up and configure a simple VOIP network, we will select the following devices:

 router model 2811 (works as Call Manager Express),

 a switch model 2960 (works as a switch),

 and two IP telephones (model 7960).

Figure 5.8 Simple VOIP network topology

Configuring a simple VOIP network takes place in the following steps: Step 1. Connect the power supplies to both phones.

In addition, we change the names of the phones to: IP Phone1, IP Phone2. Step 2. Connect router A to switch B.

We connect the router interface Fa0/0 to the Fa0/24 interface of the switch with an Ethernet cable.

Step 3. Connect IP Phone 1 to switch B.

Connect the phone's Fa interface (note: two ports will appear on the screen, one named Switch and the other PC - choose either one) to the switch's Fa0/1 interface using an Ethernet cable.

Step 4. We configure the IP address for interface Fa0/0 of router A. To do this, we execute the following commands:

conf t

hostname A

int Fa0/0

ip address 192.168.1.1 255.255.255.0

no shutdown

Step 5. We configure the DHCP service on router A.

To do this, we run the following commands:

conf t

ip dhcp pool POOL

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

option 150 ip 192.168.1.1

Step 6. We configure the Call Manager Express telephony service on the router To do this, we enter global configuration mode (execute the following commands): en

conf t

Assuming that a maximum of 5 phones will be supported on our network. We enter the telephone service configuration mode using the command:

telephony-service

In the telephone service configuration mode, the following options are set: max-dn 5

max-ephones 5

ip source-address 192.168.1.1 port 2000

Below we can read a brief description of the purpose of the commands:

 max-dn – is used to set the maximum number of directory entries (so-called directory names) that will store information about telephone numbers,

 max-ephones – is used to set the maximum number of IP phones,

 ip source-address <source_address> port

<port_no> - defines IP address and the source port number for telephone services,

Step 7. We configure the VLAN on switch B.

Since we established in the previous step that we will support a maximum of 5 phones, we need 5 ports on the switch.

need to configure them to carry voice on VLAN 1. To do this, we run the commands: conf t

hostname B

interface range fa0/1-fa0/5

switchport mode access

switchport voice vlan 1

Step 8. On router A, we assign telephone numbers to both phones. Now we create directory entries (called directory names). To perform this step we will use the commands:

en

conf t

ephone-dn 1

number 101

exit

ephone-dn 2

number 102

end

Figure 5.9 Configuring phone numbers in Call Manager Express Step 9. We check that IP Phone1 has received an IP address and number. Note: the process of receiving the line number address can take up to several minutes. Call Manager Express needs to register the configured phones. Correct registration manifests itself in the form of messages in the router. This is shown in the following figure.

Figure 5.10 Correct registration of telephone numbers in Call Manager Express To check whether IP Phone1 has been given the correct IP address and line number, move the mouse pointer over the phone and check the data that appears.

Figure 5.11 Current configuration of IP Phone1.

Step 10. Connect IP Phone 2 to switch B.

We connect the Fa interface of the phone to the Fa0/2 interface of the switch using an Ethernet cable. Check that the IP Phone2 has obtained the correct IP address and line number. To do this, move the mouse pointer to the phone and check the data that appears.

Figure 5.12 Current configuration of IP Phone2.

In addition, on the console of router A using the command: show ip dhcp binding , we can check the status of the assigned IP addresses.

Figure 5.13 Status of dynamically assigned IP addresses

Step 11. We check the connectivity between the IP phones.

We have reached the last step, which is to check if it is possible to call number 102 from number 101 and vice versa. To do this, we click IP Phone1. The phone number (101) appears in the top right corner on the display panel.

Figure 5.14 Display panel on phone number 101

If we want to call the number of the second telephone 102, we remove the handset (simply click it). You will hear a continuous tone confirming the call to the telephone exchange.

Figure 5.15 The phone is now ready for dialing.

The display will show "Enter number". We proceed to dial the number. On IP Phone1 you dial 102, on IP Phone2 you hear a ring tone.

Figure 5.16 Phone 101 calls Phone 102.

Now we can hang up and call from the second phone (number 102) to the number of the first phone, i.e. 101. At the same time, on display of Phone 102 we can observe that the message "From: 101". This message informs us that this is an incoming call from the number 101.

5.6 Communication between Two VoIP Exchanges In order to set up and configure two VOIP networks (exchanges), connected between each other, we will first perform the following topology:

Figure 5.17 VoIP network topology with two exchanges A and C. To create the topology, we choose:

 two routers (model 2811),

 two switches (model 2960),

 four IP telephones (model 7960).

Assumptions for the configuration:

The assumptions for this example are shown in the table below.

Table 5.1 Assumptions for the configuration of a VoIP network with two PBXs. We will configure two VoIP PBXs in two stages :

 Stage 1 – internal (local) configuration of phones and exchanges.

 Stage 2 - configuring the link between the exchanges.

Stage 1 - Configuring the phones and PBXs.

We will carry out Stage 1 using the following steps:

Step 1. We connect the power supplies to the telephones at PBXs A and C. Step 2. We connect PBX A to switch B.

Step 3. Connect PBX C to switch D.

Step 4. Connect IP Phone 1 and IP Phone 2 to switch B.

Step 5. Connect IP Phone 3 and IP Phone 4 to switch D.

Step 6. We configure the IP address for interface Fa0/0 of PBX A. To do this, perform the following commands:

conf t

hostname A

int Fa0/0

ip address 192.168.1.1 255.255.255.0

no shutdown

Step 7. We configure the IP address for interface Fa0/1 of PBX A. To do this, we execute the following commands:

conf t

hostname A

int Fa0/1

ip address 10.0.0.1 255.0.0.0

no shutdown

Step 8. We configure the DHCP service on PBX A with option 150. To do this, we execute the following commands:

conf t

ip dhcp pool VOICE1

network 192.168.1.0 255.255.255.0

default-router 192.168.1.1

option 150 ip 192.168.1.1

Step 9. We configure the IP address for interface Fa0/0 of panel C. To do this, we execute the following commands:

conf t

hostname C

int Fa0/0

ip address 192.168.2.1 255.255.255.0

no shutdown

Step10. We configure the IP address for interface Fa0/1 of the C panel. To do this, we execute the following commands:

conf t

hostname C

int Fa0/1

ip address 10.0.0.2 255.0.0.0

no shutdown

Step 11. We configure the DHCP service on PBX C with option 150. To do this, we execute the following commands:

conf t

ip dhcp pool VOICE2

network 192.168.2.0 255.255.255.0

default-router 192.168.2.1

option 150 ip 192.168.2.1

Step 12. We configure the Call Manager Express telephony service on PBX A. To do this, we enter global configuration mode and execute the following commands: en

conf t

telephony-service

max-dn 5

max-ephones 5

ip source-address 192.168.1.1 port 2000

Step 13. We configure the Call Manager Express telephony service on PBX C. To do this, we enter global configuration mode and execute the following commands: en

conf t

telephony-service

max-dn 5

max-ephones 5

ip source-address 192.168.2.1 port 2000

Step 14. On PBX A, we assign telephone numbers.

We now create directory entries (so-called directory names) for PBX A, using the commands: ephone-dn and number . We then create the phone line assignments for the directory entries.

We assign telephone line 1 of the first telephone found by DHCP to directory entry ephone-dn 1 (i.e. number 101). We assign phone line 2 of the second phone found by DHCP to the ephone-dn 2 directory entry (i.e. number 102).

We will use commands to perform this step:

en

conf t

ephone-dn 1

number 101

ephone-dn 2

number 102

end

Step 15. On PBX C we assign telephone numbers.

As with PBX A, we now create directory entries (so-called directory names) for PBX C, using the ephone-dn and number commands. We then create the phone line assignments for the directory entries.

We assign telephone line number 1 of the first telephone found by DHCP to directory entry ephone-dn 1 (i.e. number 581). We assign phone line 1 of the second phone found by DHCP to the ephone-dn 2 directory entry (that is, number 582). To perform this step we will use the commands:

en

conf t

ephone-dn 1

number 581

ephone-dn 2

number 582

end

Step 16. We configure the VLAN on switches B and D.

To do this, we execute the commands:

conf t

hostname B

interface range fa0/1-fa0/5

switchport mode access

switchport voice vlan 1

conf t

hostname D

interface range fa0/1-fa0/5

switchport mode access

switchport voice vlan 1

Stage 2 – configuring the link between A and C exchanges We will carry out stage two, the configuration of the inter-panel link, using the following steps.

Step 1. At PBX A, we configure a static route to PBX C.

To do this, we execute the commands:

en

conf t

ip route 192.168.2.0 255.255.255.0 FastEthernet0/1

Figure 5.18 Static routes in router A.

Step 2. At PBX A, we configure the processing of VoIP traffic to PBX C. To do this, we execute the commands:

en

conf t

dial-peer voice 1 voip

destination-pattern 58.

session target ipv4:10.0.0.2

end

Note: here we also configure the number prefix to PBX C (58). The dot that follows the prefix is important - it stands for a single digit from 0 to 9.

Figure 5.19 Configuring VoIP traffic from router A to router C. Step 3. At PBX C, we configure a static route to PBX A.

To do this, we execute the commands:

en

conf t

ip route 192.168.1.0 255.255.255.0 FastEthernet0/1

Figure 5.20 Static routes in router C .

Step 4. In PBX C, we configure the processing of VoIP traffic to PBX A. To do this, we execute the commands:

en

conf t

dial-peer voice 1 voip

destination-pattern 10.

session target ipv4:10.0.0.1

end

Note: here we also configure the number prefix to PBX C (10). The dot that follows the prefix is important - it stands for a single digit from 0 to 9.

Figure 5.21 Configuring VoIP traffic from router C to router A. Step 5.We check the communication between IP phones belonging to different exchanges. We can now check whether phones located in different exchanges can call each other. To carry out a communication check of the phone located in PBX A (101) to the phone located in PBX C (582), we will dial the phone number 101, which will call the phone number

582.

Figure 5.22 Phone 101 is calling Phone 582.

Figure 5.23 Phone 101 is connected with phone 582.