SHAPING THE FUTURE OF SATELLITE COMMUNICATIONS
On a modem (or modulator, or demodulator) the satellite subnet is
split into different IP ranges, while this partitioning is not known to
the routers and the PCs inside the satellite subnet.
This behavior is achieved because the modems perform proxy-
ARP for all IP addresses inside the remote subnet that are at the
other side of the satellite link(s).
In this example we refer to Figure 4, the configuration for the HUB uses VLANs,
and the configuration for the remote sites is without VLANs. Both options are
possible. Some more words about the configuration in the picture:
2.1.2.4 HUB Router Configuration:
The HUB router has an IP interface in the satellite subnet: 10.0.0.1/24.
Further it has routes that point to the remote network.
These routes have the 'SITE router' as next HOP IP address.
2.1.2.5 HUB Modem Configuration:
The modem has an 'IP interface' on VLAN 5:
A local subnet on VLAN 5: 10.0.0.2/29: This means that there has been a local IP
address assigned (10.0.0.2) and that the IP range 10.0.0.2/29 can be reached
locally (at this side of the satellite link).
A remote subnet: 10.0.0.0/24. This means that IP range 10.0.0.0/24 except the
local subnet is at the other side of the satellite link: A longest prefix match
algorithm excludes the local subnet from remote subnet, because the local subnet
has in this case a longer subnet prefix (/29 instead of /24).
A gateway (= 10.0.0.1) on VLAN 5, to reach the IP addresses that are outside the
local subnet. Each VLAN is a separate routing domain (separate VRF), so each
VLAN has its own gateway.
Besides an 'IP interface entry' on this VLAN, we must create routes from the
Ethernet interface to the satellite link, and routes from the satellite link to the
Ethernet network. The Ethernet RX route table contains routes that direct traffic
from the Ethernet link to a given PID or ISI on the modulator.
The Demodulator RX route table contains routes that direct traffic from a PID or ISI
on the satellite link to a VLAN on the Ethernet interface.
2.1.2.6 SITE Router Configuration:
This configuration is similar to the HUB router configuration, but without VLANs.
2.1.2.7 SITE Modem Configuration:
This configuration is similar to the HUB modem configuration, but without VLANs.
To Next Page
Loading...
