Q-Flex Satellite Modem Installation and Operating Handbook
7-19
7.8 IP Functionality
7.8.1 Base Modem IP
As shown in
Figure 7-10
, the modem has one RJ45 auto-sensing Gigabit Ethernet port for
M&C and one for sending and receiving satellite IP traffic. (A 4-port Gigabit Ethernet switch
is available as an option.)
Figure 7-10 Modem Ethernet Ports
Both of the Ethernet connections by default form part of an Ethernet bridge and share an IP
address. Essentially, the bridge makes the modem disappear from the network in relation to
passing IP traffic over a satellite. Consequently, for simple point-to-point communications,
little or no user set up is required to pass IP traffic over satellite. If both Ethernet ports are
configured to be part of the bridge then a single Ethernet connection to the modem can be
used for both IP traffic and modem M&C control (using either of the two RJ45 connectors). If
the M&C port is configured to be outside the bridge then one Ethernet port is dedicated to IP
traffic and the other to M&C control (as labeled on the connectors).
To communicate with the modem itself for M&C purposes, an IP address and subnet mask
must be set. Note that setting an IP address to 0.0.0.0 causes the modem to request an IP
address from a Dynamic Host Control Porotocol (DHCP) server on the network. Static routes
are supported allowing routing decisions to be made based on a set of explicit routing rules
that can be entered via the web user interface. Dynamic routing is also supported.
The use of a default gateway IP address is supported. When a gateway is specified then it
provides a next-hop IP address for all destinations that are not on the local subnet. This is
usually the address of a router that has been set up to forward packets to the correct
network.
The bridge maintains information on how to forward frames based on replies that are
received from each device in the network.
The M&C port can be taken out of the bridge (via the ‘
Bridge M&C port
’ menu option) in
which case each port has its own IP address.