Comtech EF Data CRS-180 - Manual (Page 31)

CRS-180 70/140 MHz IF 1:1 Redundancy Switch MN/CRS180.IOM
Introduction Revision 11
1–11
Ethernet hub allows LAN-to-WAN traffic to continue even after a switchover occurs since both
modems will be receiving the LAN traffic.
In Managed Switch Mode, both modems should be assigned a unique Management IP address
on the same subnet in order to share the parameter file.
Router Mode: For the CDM-570/A in Router Mode, you should use an external Ethernet switch.
Router mode does not require a “dumb” hub as with Managed Switch Mode and, for
performance reasons, an Ethernet switch is highly recommended.
In Router Mode, both modems must be assigned a unique Management IP address on the same
subnet (172.18.10.21/24 and 172.18.10.22/24 as shown in Figure 1-8 and Figure 1-9). This is
used to share the param file. A Traffic IP address on the subnet must also be assigned
(172.18.10.20/24) in the Online modem.
Whichever modem is Online will assume the Traffic IP. When there is a switchover to the
backup modem, this modem will now assume the Traffic IP. As shown in Figure 1-9, the backup
modem will also broadcast a “gratuitous ARP” that will tell all local devices to now associate a
new MAC address for the Traffic IP 172.18.10.20. Each device will update their ARP tables and
traffic will resume virtually instantaneously.