Comtech EF Data CDM-570 - Manual (Page 210)

CDM-570/570L Satellite Modem with Optional IP Module Revision 12
Ethernet IP Module Interface MN/CDM570L.IOM
13–4
13.3.9 Managed Switch Mode
Managed Switch Mode is the Comtech EF Data IP modem intelligent networking solution that
allows a link to be setup with minimal configuration (no specific routes need to be configured).
The IP Module also supports non-IP traffic with Managed Switch Mode. All IP traffic will be
subject to user-configured QoS restrictions.
13.3.9.1 Managed Switch Mode Operation
1. Managed Switch Mode will automatically use Header Compression for
compressing Layer 2 (even if Header Compression option has not been
purchased). Because of this, some of the initial traffic sent between two
devices will not be received over the satellite until a full Header is
transmitted. For example, the default Header Compression Refresh Rate is
50 packets. If a ping is sent over the satellite, then it will time out until the
full Header packet is sent. The Header Compression Refresh Rate on the
Administration Menu can be reduced to minimize the amount of traffic lost
when traffic is first sent between two devices. Once communication
between two devices has been established, both IP modems will be able
to receive all traffic, unless one IP modem is power cycled or reset.
Header Compression feature should be enabled for compressing Layer 3,
Layer 4 and Layer 5.
2. Do not enable IF Loopback (or link the TX to RX by a BNC cable or
satellite) on an IP modem operating in Managed Switch Mode when
connected to a LAN. In this configuration, Managed Switch Mode will
resend all Layer 2 broadcast packets and cause a “broadcast storm” on
the LAN. To perform a loop test to verify the modem or satellite link, do
one of the following:
a) Reconfigure the CDM-570/570L interface selection: From the front
panel, select Config Æ Intfc, and then select RS422, V.35, or RS232.
- OR –
b) Set the IP Module 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-570/570L 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.