Comtech EF Data VMS v3.12.x Vipersat - Manual (Page 234)

Network MN/22156, rev 12
4-16 VMS User Guide
unusually large sites, allowing an additional layer of NAT without requiring
any more explicit routing within the Vipersat Modem Routers.
The Series800 satellite modems are basically two-port routers, with one port to
the LAN (Ethernet) and the other to the WAN (satellite network). Therefore,
very little dynamic decision making is necessary, and most routing is done using
static routes. These routes can be entered to route IP traffic either over the satel-
lite or to another device on the local network.
Route definitions vary depending on which of the three units in the product
series is being configured. Each of these unit types perform a unique role:
• The CDM-800 is a Hub unit that serves as a forwarding router, and
requires explicit route definitions for each of its Remote units (satellite
WAN), as well as a default gateway to the Ethernet LAN. For WAN
traffic, GSE labeling is applied and the data is forwarded per the table
entries.
• The CDD-880 is a Hub unit that receives traffic off the WAN and
forwards all packets to its default gateway (to LAN).
• The CDM-840 serves as the Remote modem unit that filters received
satellite WAN transmissions based on GSE labeling and routes packets
destined for the Ethernet LAN. LAN traffic received from its subnet is
forwarded using the lone default route to the WAN.
Default gateways are defined as the route of last resort. Typically, the IP address
of the next hop router in the network is specified here.
Refer to the CDX-8XX Installation and Operation Manual for additional infor-
mation on entering routes.
Creating the Static Routes
The following procedure outlines the basic route structure that the target
Series800 unit will require for its role in the network.
One of the key routes that must be created is a default gateway address for rout-
ing the data traffic that is received by the unit.
In a Hub configuration, the default route will typically point to a router on
the same LAN as the Hub unit. In the example shown in the below figure,
that router is specified as the Next Hop address 10.1.0.1.
In a Remote configuration, the default route will typically point to the satel-
lite modem (WAN) used for communications back to the Hub.