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Advice for Setting Backplane Connections and Avoiding Loops

Considerable care should be taken when setting backplane

connections if there is more than one Switch 1005 installed in you r

MSH chassis. If more than one module has multiple connections

enabled on the same VLAN, a network loop can occur, severely

affecting network operation.

For example, consider a pair of Switch modules wh ere all four

backplane connections are enabled and in the same VLAN. If a packet

with a unicast destination address arrives on the backplane E1,

destined for an end-station on backplane E2, both Switch modules will

independently switch the packet onto E2, resu lting in duplication.

Packets with broadcast destination addresses will loop conti nuously

between the two Switch modules. You can avoid this situation by

following these guidelines:

■

If all ports on your network are in the same VLAN, you should connect

all Switch 1005 modules via the Fast Ethernet c onnection, but only

connect the internal Ethernet backplanes on on e Switch 1005.

■

Alternatively, balance the load on your Switch 1005 modules more

effectively by connecting one internal Ethernet connection to each

Switch 1005.

■

If you have implemented multiple VLANs, put ea ch internal Ethernet

connection in a different VLAN on each Switch.