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CRS-300 1:10 Redundancy Switch
Appendix A
Figure A-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.
A.3.2
Ethernet Redundancy with CRS-300
After the customer has determined the best configuration for near-to-far end Ethernet
networks, the CRS-300 1:10 Redundancy Switch may now be added to one or both ends of the
link(s). Ethernet redundancy using the CRS-300 can be accomplished using a wired-thru or
wired-around configuration.
A.3.2.1 Wired-thru Connection
This redundancy approach is the recommended and preferred
method.
The wired-thru Ethernet connection on the CRS-300 is the easiest and simplest choice for Ethernet
redundancy. This connection method – the same as used on the standard serial data interface –
provides a single connection for the User Data Interface and provides simple form-C relays that
route the Ethernet connection from your connection to either the Traffic or Redundant Modem.
A.3.2.2 Wired-around Connection
While this redundancy approach is not recommended , it can be used after study
of the LAN and WAN sides of the IP networks.
Use the wired-around Ethernet connection with the CRS-300 and the CDM-700 modem where
both modem data interface slots are needed; e.g., where one slot is HSSI or G.703 and the other
slot is GigE. With the Ethernet slot configured for the wired-around method, this gives full
redundancy capability to both data slots. However, care must be taken to ensure there are no
Ethernet network loops or connection problems – this method should only be used if both
modem data slots are used. In general, the wired-around approach can be used in a hub-to-
remotes configuration with standard traffic.
A–3
MN/CRS300.IOM
Revision 19
connection
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