Quantum and Evolution Series Installation and Operating Handbook
8-36
the IP traffic port of the base modem is replaced by the ports on the IP traffic card (see
picture below).
IP Traffic Card Dual 10/100/1000 Base-T Ethernet Ports
8.12.2 IP Addressing
The two ports on the IP card are bridged together, acting as a two-port switch. This is true
regardless of what bridging or routing mode is selected. In bridging mode, IP addresses are
not used so there is no restriction on what subnets are off the two traffic card ports. In
routing mode, since the IP traffic card has a single address covering both ports, there can
only ever be one direct subnet off the two ports.
•
With an IP card fitted and the base modem M&C port out of the bridge then the base
modem IP traffic port is not addressable.
•
With an IP card fitted and the two base modem ports bridged then base modem
access can be used for M&C only – no base modem data will be passed over satellite.
•
If no IP traffic card is fitted and the M&C port is out of the bridge (i.e. the traffic port has
its own IP address) then the IP traffic port and M&C port
must
be on different subnets
because otherwise the modem does not know which of the two ports to respond out of.
8.12.2.1 Gateways
The key to understanding the default gateways on the modems is being aware that there is
one TCP/IP stack running on a processor on the base modem and, if fitted, one TCP/IP
running on a processor on the IP Traffic card
and that there can only ever be one gateway
associated with each TCP/IP stack in operation even although the modem menus support
three gateways
:
•
M&C
gateway
•
Traffic port gateway
•
Satellite port gateway
The traffic port gateway is
never
used unless an IP traffic card is fitted. The satellite port
gateway is
never
used unless routing mode is selected. You can
never
set both a traffic
port gateway and a satellite port gateway at the same time because the software
controlling the associated IP features is running on a single TCP/IP stack.
In routing mode you can set either the satellite gateway or the IP traffic gateway. It is
undefined which will be used if you attempt to set both!
There are no hard and fast rules for setting gateways, but if there is a single router then:
•
On the modem local to the router the IP traffic gateway will normally be used to
point to the router;
