Eurotech 930150-4003R, User Manual

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ZyWAN-G9 - User Manual
50 110150-4002A
Using Default Gateway, DHCP, and DNS
The ZyWAN-G9 provides two Ethernet (eth0, eth1), WiFi (eth2), and cellular (ppp0, ppp1) interfaces.
Each of these interfaces can potentially have a Default Gateway address, DHCP, and DNS server
addresses. One of these interfaces will be made the default route to reach addresses that are not
otherwise available on its local networks.
Configuration Options
The Ethernet interfaces can be configured to be a DHCP client on an existing network (the Use Dhcp
Client? option set to Yes
). The WiFi interface can be configured in similar manner (in “managed
mode”). In this case, it is likely that the ZyWAN-G9 will obtain a Default Gateway and DNS server from
the network to which it is attached.
Static IP addresses may also be configured. This allows the Ethernet or WiFi to be configured with a
Default Gateway and one or two DNS Server addresses for the interface. These items may be left
blank if there is no server available or if it does not make sense to include them in the configuration.
When configured with a static IP address, the Ethernet interface may be configured to
Run DHCP
Server . This will allow the ZyWAN-G9 to assign an IP address to other devices on the network. The
WiFi in
terface in “master” mode defaults to static IP and also provides a DHCP server to wireless
clients.
Default Route
The ZyWAN-G9 will make one of its interfaces the default route based on the configuration and the
availability of each network. The order of preference for the default route is:

Ethernet 0 (eth0)

Ethernet 1 (eth1)

WiFi (eth2)

Cellular (ppp0, ppp1)
The first interface which has a Default Gateway (static configuration in Web page, or obtained
dynamically from a DHCP server) will be the one used for the ZyWAN-G9
‟s default gateway. If the
Ethernet cable is unplugged or the WiFi is 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 Default Gateway (configured explicitly in the ZyWAN-G9 Web configuration or
obtained from a DHCP server) will interfere with the intended operation. Therefore, care needs to be
taken to avoid this situation. For instance, this may require disabling or setting the Ethernet and WiFi
to static IP addresses without the Default Gateway (leaving it blank), to allow the PPP interface to
become the default gateway.
DHCP Server and NAT
If either the Ethernet or WiFi (master mode) is running as a DHCP server, then the ZyWAN-G9 will
respond to any client device on the network that requests an IP address. The ZyWAN-G9 will assign
the device an address in accordance with the list of addresses specified in the ZyWAN-G9 Web
configuration. The client device will use the ZyWAN-G9
‟s network address as its Default Gateway.
Thus, if the ZyWAN-G9 is used on a local network where another DHCP server is already running, the
Run DHCP Server option should generally be set to No .
The
Open Ports section on the Networking page must include UDP port 67 to allow DHCP traffic to the
ZyWAN-G9.