Comtech EF Data CDM-570A - Manual (Page 471)

CDM-570L/570AL Satellite Modem with Optional Packet Processor MN-CDM570A
Appendix D Revision 2
D–13
A. Reconfigure the CDM-570A/570AL-IP interface selection: From the front
panel, select Config Intfc, and then select RS422, V.35, or RS232.
- OR –
B. Set the Packet Processor to Router Mode.
Information about the function of Managed Switch Mode, as well as a detailed description for
the setup and configuration of a Managed Switch Mode pair, is as follows:
• Because Managed Switch Mode is a “smart wire,” the devices attached to it on either side of
the satellite should be on the same subnet and should not configure a next hop address to
be the CDM-570A/570AL-IP address (as should be done with router mode). For purposes of
configuration, Managed Switch Mode should be viewed to function in much the same way
as a bridge (however, without spanning tree protocol).
• All of the features that groom and optimize the satellite link in router mode are also
available in Managed Switch Mode.
• Managed Switch Mode Multicast Option – Multicast packets in Managed Switch Mode are
identified using multicast MAC address. These identified multicast packets are either routed
or dropped based on the Managed Switch Mode multicast option.
• Managed Switch Mode uses Layer 2 (MAC) addresses to learn where to send packets. In
comparison, router mode uses the destination IP address in the packet in conjunction with
the route table to determine where to forward the packets.
• The Packet Processor in Managed Switch Mode is configured to be in promiscuous mode
with a data rate of 10/100BaseT Half Duplex/Full Duplex. The Packet Processor needs to be
in promiscuous mode in order to learn the attached networking devices.
• Since Managed Switch Mode does not use a routing table, the determination of where to
send a packet is made by a learning process. When the system is powered-up, all packets
from each subnet (local and remote) will be sent over the satellite interface. However, as
each Packet Processor learns which devices are attached to their local Ethernet interfaces,
the Packet Processor begins to filter packets which it has learned are locally attached to its
Ethernet interface.
• The Managed Switch Mode learning/forwarding algorithm is as follows:
o If the packet is destined for the Packet Processor, then process it locally.
o If the packet is from the Packet Processor Interface, then send it to the Satellite
interface; OR if the destination Layer 2 (MAC) address of the packets matches the
source Layer 2 address for a packet we have already seen, then the destination MAC
address of this packet is on our local subnet; so why send it over the satellite interface.
In this case, the Packet Processor will drop the packet.
o If the packet is from the satellite interface, then send it out the Ethernet interface.