Comtech EF Data CDM-625A Installation And Operation Manual page 654

CDM-625A Advanced Satellite Modem
Appendix K
K.2.3.2 Networking Loops in Router Mode (with IP Packet Processor)
Figure K-7. Point-to-Point Configuration in "Router Multipoint Hub" Working Mode
In a network where more than one CDM-625A's working mode is set to "Router Multipoint
Hub", care must be taken in route table configuration to avoid Ethernet Networking Loops.
Figure K-7 shows Point-to-Multipoint configuration using the optional IP Packet Processor.
When a CDM-625A's working mode is configured as "Router Multipoint Hub", the modem is
allowed to egress on the WAN interface the same packet as was originally ingressed from the
WAN interface. This is necessary to allow the Point-to-Multipoint configuration.
However, configuring more than one modem as a Router Hub across the WAN Interface, then
adding default routes on either side – or any other invalid routes – will cause the same packet to
ping-pong between these two modems until TTL times out.
K–6
MN-CDM625A
Revision 4