Aim of the guide

The aim of this guide is to demonstrate a solution for providing telephone communication to a small business or isolated branch office with a small number (up to 250) of subscribers.

To connect to the PSTN, SIP protocol connections are used via an operator providing a trusted Ethernet interface.

Using the SMG-500 IP PBX by Eltex is optimal for this task.

Proposed network diagrams


Logical network diagram	Physical network diagram

Description of diagrams

The telephony core is SMG-500 IP PBX with M8O submodules.

IP phones are registered on the SMG-500 via a network of Ethernet switches.

Analog phones are connected to IP PBX via subscriber gateways, such as TAU-36.IP.

The subscriber gateway is connected to IP PBX via an Ethernet network. Subscribers are registered on the PBX via SIP.

Used types of Ethernet ports

The following Ethernet interface names are used in this guide:

Port designation	Port purpose	Port requirements
A1	SMG-500 IP PBX connection port	Trunk port with specified native VLAN
Px	IP phone connection ports	Access port with Voice VLAN and PoE
U1	Port for connecting to an IP telephony provider	Access or trunk port
Tx	Ports for connecting analog TAU gateways	Access port
M1	Port for connecting AWS, which is used to configure and manage an IP PBX and phones.	Access port

Used VLANs

In the guide, the following virtual local area networks (VLAN) are used.

VLAN name	VLAN purpose	Ports included in VLAN
Mgm_Vlan	PBX management	A1 – untagged M1 – untagged
Data_Vlan	Telephony signalling and media traffic	A1 – tagged Px – voice VLAN Tx – untagged
Provider_Vlan	Link towards the provider	U1 - tagged or untagged

Traffic restrictions between VLANs

The necessary permissions for this example are listed in the table:

From \ To	Data_Vlan	Provider_Vlan
Mgm_Vlan	Allow HTTP, HTTPS
Data_Vlan		Allow SIP, RTP from the A1 host to the U1 host
Provider_Vlan	Allow SIP, RTP from the U1 host to the A1 host

IP addressing and dial plan

For demonstration purposes, this guide will use the following:

Dial plan:

Internal phones:
1. Three-digit dial: xxx
2. Numbers used in the example: 200 – 419
3. Numbers 380 through 415 inclusive are assigned to subscribers with analog telephones connected via TAU-36.IP.
PSTN phones:
1. Area code (383). Within the area, seven digits: xxxxxxx
2. Our office has been assigned the following numbers: (383)9741001 – 9741010
3. Incoming calls from the PSTN to numbers 974100x are forwarded to internal 20x numbers accordingly.
4. The number 9741010 is used for outgoing PSTN calls for subscribers who do not have a connected local number.

IP addressing:

Telephony network (Data_Vlan):
1. Network: 192.0.2.0/24
2. VLAN ID: 92
3. Default gateway: 192.0.2.1
4. SMG-500 IP PBX: 192.0.2.10
5. TAU-36.IP subscriber gateway: 192.0.2.16
6. IP phones: 192.0.2.20 192.0.2.240
Management network (Mgm_Vlan):
1. Network: 192.168.1.0/24
2. SMG-500 IP PBX: 192.168.1.10
Provider connection network (Provider_Vlan):
1. Network: 198.51.100.0/28
2. Provider's IP PBX: 198.51.100.1
Addresses of services:
1. NTP server: 192.0.2.1

Tables for configuration are available via the link.

Before configuring IP telephony, ensure that the data network is functioning properly. Check the network connectivity.

Equipment configuration

SMG has a dynamic firewall enabled by default, which automatically blocks device access in case of multiple unsuccessful authorization attempts. This may be inconvenient during the configuration process. It is recommended to disable the dynamic firewall according to the instructions before starting the configuration. It is recommended to enable the dynamic firewall after completing the configuration for security reasons.

Minimum required configuration

Configuring IP PBX

The SMG-500 IP PBX is configured via a web interface. Default account details:

Username: admin
Password: rootpasswd

The necessary IP PBX configuration includes the following steps:

Configuring the management interface

Follow the instructions to change the IP settings on the main interface. Specify:

Network name: Mgm_Vlan
IP address: 192.168.1.10
Netowrk mask: 255.255.255.0
Gateway: 0.0.0.0 – the gateway will not be used for this interface.
Disable all services except “Web Management”.

Adding an interface for telephony

Follow the instructions to add and configure an interface for RTP and SIP traffic:

Network name: Data_Vlan
VLAN ID: 92
IP address: 192.0.2.10
Network mask: 255.255.255.0
Gateway: 192.0.2.1
Check the “SIP signaling” and “Forward RTP” boxes.

Configuring network parameters

Follow the instructions to change the used interface gateway to

Configuring date and time

For IP telephony to function correctly, set the current date and time on the device.

Time and date are configured on an NTP server.

For automatic time synchronization via NTP on SMG-500, the NTP server on the ESR router or L3 MES switch with the 192.0.2.1 address is used.

To configure NTP synchronization, use the instructions to specify the NTP server address:

Time server (NTP): 192.0.2.1
Time zone: select the required time zone.

Creating an SIP profile

Follow the instructions to create a SIP profile.

In the “Name” field, enter “SIP subscribers”.

In the “Network interface for SIP” and “Network interface for RTP” fields, select

Creating SIP subscribers

Follow the instructions to create SIP subscribers. When creating, specify:

Number of subscribers: 220
Starting number: 200
SIP profile: SIP subscribers.
Password: 1234

Configuring a DHCP server

IP phones require IP addresses to operate. These can be configured manually on each device or assigned using a DHCP server. Configure the DHCP server according to the instructions.

Specify the following parameters:

Source address: 192.0.2.20
Destination address: 192.0.2.240
Subnet mask: 255.255.255.0
Gateway/router address: 192.0.2.1

Saving the configuration

After completing the initial configuration, it is recommended to save the device configuration.

Configuring the connection to PSTN

To connect the company's telephone network to the public telephone network, it is necessary to configure the trunk to the PBX and configure the routing of calls from and to the city. For incoming routing, the B number will also need to be modified to connect an external number such as 73831234567 to one of the internal numbers. For outgoing routing, the A number will need to be modified to an external number.

Creating a SIP interface for accessing PSTN

Follow the instructions to create a SIP interface. When creating it, specify:

Trunk group:
1. Name: TG to PSTN.
SIP interface:
1. Name: to PSTN.
2. Trunk group: TG to PSTN.
3. Host name/IP address: 198.51.100.1
4. In the “Signaling network interface” and “Network interface for RTP” fields, select

Configuring the modification of incoming call numbers from the PSTN

Following the instructions, create a table of modifiers named “B-number substitution from PBX”.

Following the instructions, create a B-number modification for calls from PBX in the “B-number substitution from PBX” modifier table. When creating, specify:

Number mask: (7383974100[1-9])
Modification rule for CdPN/Original CdPN: --------20$

Following the instructions, assign the modification to the trunk group. When creating, specify:

Add: CdPN
CdPN: Replacement of B-number from PSTN.

Configuring routing to PSTN numbers

Follow the instructions to create a prefix in the dial plan. When creating, specify:

Name: to PSTN.
Trunk group: TG to PSTN.
Mask: (xxxxxxx|[78][3489]xxxxxxxxx|810x.)

Configuring routing to PSTN numbers

Following the instructions, create a modifier table named “B-number in E.164”.

Following the instructions, create three B-number modifications for calls to PSTN.

Modification of “local” numbers
1. Number mask: (xxxxxxx)
2. Modification rule for CdPN/Original CdPN: +7383$
Modification of long-distance numbers
1. Number mask: (8[3489]xxxxxxxxx)
2. Modification rule for CdPN/Original CdPN: 7$
Modification of international numbers
1. Number mask: (810x.)
2. Modification rule for CdPN/Original CdPN: ---$

Following the instructions, create a table of modifiers named “A-number in E.164 PSTN”.

Following the instructions, create two modifications of the A-number for calls to PSTN.

Modification of numbers 201-209 to numbers 7941001-7941009
1. Number mask: (20[1-9])
2. Modification rule for CgPN/RedirPN/Generic/Location: +738397410-$
Modification of other numbers to number 9741010
1. Number mask: (xxx)
2. Modification rule for CgPN/RedirPN/Generic/Location: +73839741010!

Follow the instructions to assign the modification to the trunk group. When creating, specify:

Add: CdPN
Add: CgPN
CdPN: B-number in Е.164
CgPN: A-number in Е.164 PSTN

Saving the SMG-500 configuration

Save the device configuration.

Connecting IP phones

VP-17P and VP-30P phones can be powered by switches using PoE technology or from a 230 V network via personal power supplies.

If the phones are turned on after completing all of the above settings, they will receive IP addresses automatically.

The first phone turned on will receive the 192.0.2.20 address, the second one will receive the 192.0.2.21 address, and so on.

If the MAC addresses of the phones are known (written on a sticker on the back of each device), it is possible to find out the correspondence between the devices and addresses by going to the “Network Services” → “DHCP Server” menu of the SMG-200 web interface. The list of MAC addresses and IP addresses is located at the bottom of the page in the “Assigned IP Addresses” table.

On the phone, the IP address can be found in “Menu” → ‘Status’ → “Network.”

The IP address of the phone will be needed to configure it via the web interface.

Configuring the phone

Follow the instructions to configure the phones.

Fill in the following fields:

Phone number: values from 200 to 267 without repetitions.
Username: value similar to the previous item.
Password: 1234
SIP proxy server: 192.0.2.10
Registration server: 192.0.2.10

Connecting analog phones

Analog phones are connected to the SMG-500 IP PBX via TAU series analog gateways.

Configuring the TAU-36.IP analog gateway

The TAU-16.IP analog gateway (referred to as TAU) is configured via the web interface in the example below.

Default IP address: 192.168.1.2
Default username: admin
Default password: rootpasswd

Proposed network diagrams


Logical network diagram	Physical network diagram

The description of diagrams

The telephony core is SMG-200 IP PBX with M8O submodules.

IP phones are registered on the SMG-200 via a network of Ethernet switches.

Analog phones are connected to IP PBX via subscriber gateways, such as TAU-16.IP.

The subscriber gateway is connected to IP PBX via an Ethernet network. Subscribers are registered on the PBX via SIP.

The SMG-200 can be equipped with one or two M8S submodules, each with 8 FXS ports. Accordingly, 8 or 16 analog phones can be connected directly to the SMG-200.