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IP address for the DNS server (PABX). The PABX system also acts as a DNS proxy in
place of the ISP DNS server.
What are IP addresses and subnetwork masks
With the initial settings IP addresses and subnetwork masks are already set for the PABX system router. Both of these
values are each 4 bytes in length.
IP address:
192.168.1.250
Subnet mask: 255.255.255.0
The IP address is an address that is reserved for private local networks.
The subnetwork defines that this is a Class C network in which up to 254 LAN clients can be linked. Using the subnet-
work mask an IP address can be divided into the network address and the host address (address of the PC).
Example with this PABX:
IP address of the
PABX:
192.168.1.250
IP netmask for the
PABX:
255.255.255.0
Network part of the
IP addresses:
192.168.1.xxx
Host part of the address: x.x.x.250
First usable
IP address:
192.168.1.1 (netmask: 255.255.255.0)
Last usable
IP address:
192. 168. 1. 254 (netmask: 255.255.255.0)
You can assign the available IP addresses to the individual LAN clients manually, or have them assigned by the PABX
system via DHCP. No IP address may be used simultaneously by more than one client however. With regard to the
example given above this means that the address 192.168.1.250 may not be allocated again, as it is already being used
by the PABX system.
The network part of the IP address may not be changed, as otherwise the LAN clients would not all be located within
the same IP network. A PC with the IP address 192.168.2. 1 is located in a different network. A PC from the PABX net
would not be able to locate this other PC if it is not within its own network.
In addition, the same subnetwork mask must also be entered at all LAN clients located within the same network.
Router functions
Automatic Internet access, fallback
Several ISPs (ISP – Internet Service Provider) can be set up in the PABX. Connectivity to the Internet is provided via
the WAN port (e.g. DSL port), or via an ISDN port. If required, connection to the Internet can be set up automatically.
If your selected ISP is not available, the next ISP in the list will be selected automatically.
Short Hold
Short Hold means that the PABX system terminates the Internet connection automatically after a configurable time
period when there is no exchange of data from/to the Internet (inactivity). You can set this time separately for each
ISP that you have configured.
This can result in increased connection costs with frequent, short excursions into the Internet, for example for pi-
cking up e-mails, as the connection is always maintained for the duration of the set holding time.
Dynamic ISDN
Higher data transfer rates can also be achieved for Internet access via the ISDN connection by bundling the two B
channels for the connection. If an Internet connection with channel bundling is active and a B channel is needed for
telephony or fax messages, one B channel is disconnected from the Internet connection. On completion of the voice
Introduction Router functions
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