Arcom ZyWAN Manuel d'utilisateur télécharger pdf (Page 41)

ZyWAN User Manual Configuring the ZyWAN

The first interface which has a Default Gateway (static configuration in Web page, or

dynamically obtained with DHCP) will be the one used for the ZyWAN’s default

gateway. If the network cable is unplugged or the WiFi becomes unavailable, the list of

interfaces is checked again, and the first available interface will be selected dynamically

as the default route, in order of preference.

This means, for instance, that if an application requires the cellular network to be the

default gateway for network traffic, any static Default Gateway (in the ZyWAN Web

configuration) or gateway obtained from DHCP will interfere with the intended

operation.

DHCP Server and NAT

If either the Ethernet or WiFi (master or ad-hoc mode) is running a DHCP server, then

the ZyWAN will reply to any device on the network that asks for an IP address using

DHCP protocol. The ZyWAN will give the device an address in accordance with the list

of addresses specified in the ZyWAN Web configuration. The device will be supplied

the ZyWAN’s network address as its Default Gateway.

The ZyWAN is able to act as a gateway, but in order to route traffic from one interface

to another, there must also be a NAT entry configured on the Networking page to route

from the source network to the destination network. The “Open Ports” section on the

Networking page must include UDP port 67 to allow DHCP traffic to the ZyWAN.

DNS Server

As a DHCP Server, the ZyWAN may also be configured to pass DNS server addresses

to other devices, so they can resolve named addresses (URL or FQDN). When this

happens, the ZyWAN will provide its own IP address as the DNS server. The ZyWAN

acts as a DNS proxy, so that any DNS requests from the client device are passed to the

one of the DNS servers known to the ZyWAN, and the resulting IP address is returned

to the client device.

In order to resolve DNS addresses, the ZyWAN needs to have a list of known DNS

server(s). It obtains the list of these servers in the same way as it obtains its default

route. The ZyWAN checks its interfaces in the preferred order: eth0, eth1, wlan0, and

ppp0. The first active interface which contains one or more DNS servers (static

address configured via the Web page, or obtained by the ZyWAN using DHCP) is used.

This list of address(es) is used by the DNS proxy. If the Ethernet cable is unplugged or

the WiFi becomes unavailable, the list of interfaces is checked again, and the first

available interface will be selected dynamically as the location for DNS servers, in order

of preference.

The “Open Ports” section on the Networking page must include UDP port 53, to allow

DNS requests to the ZyWAN.

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Arcom ZyWAN Manuel d'utilisateur Page 41