Comtech EF Data CDM-760, Installation And Operation Manual

Page: 321 / 441

Appendix D Revision 4
CDM-760 Advanced High-Speed Trunking Modem MN-CDM760
D–2
with other routers to describe or determine the best way to direct network traffic from ‘Point A’ to
‘Point B’.
D.3 Ethernet Configuration Examples
This section explains the problems with Ethernet Networking Loops , and how to properly design
applications architecture for handling Standard traffic and Split-path traffic.
Standard traffic
is
defined as Rx and Tx Ethernet traffic using the same port on the same router or switch, whereas
split-path traffic
is Rx and Tx Ethernet traffic using different ports of the same router or switch.
D.3.1 Ethernet Network Overview
When placing modems in a network, there are a number of issues that must be addressed – first
and foremost on the list of concerns is whether implementation of the switches in the network
will cause a Networking Loop . This is problematic because a Networking Loop will cause a
Broadcast Storm , which shuts down the network and causes harm to devices in that network.
Figure D-1. Networking Loop with Switches
Figure D-1 illustrates a Networking Loop with switches. The problem with this configuration is
that ‘Switch 1’ will send out an ARP request looking for a particular MAC, then each subsequent
switch passes along that request until ‘Switch 1’ receives it again. At this point, two things could
happen:
1. The switch could continue to forward all requests out all ports, creating more and more
traffic on the network until there is no bandwidth available and the switch either reboots or
locks up.
2. The switch could sense that the ARP request came back to the switch on a different port.
The switch could then stop forwarding traffic out the proper port.
Other factors will affect the network: e.g., if the switch is running Spanning Tree Protocol,
VLANs, etc.