Management and Configuration Guide K/KA/KB.15.15

Figure 68 Unicast traffic flow across DT switches
Forwarding broadcast, multicast, and unknown traffic
In the example shown in Figure 69 (page 166), multicast/broadcast/unknown traffic from Host X
or Y is always forwarded by Switch A over one of its standard 802.3ad trunk links to either Switch
B or C. Switch B or C forwards the traffic on all the links including the ISC port, but not on the port
that the traffic was received on. The peer DT switch (B or C) that receives
broadcast/multicast/unknown traffic over the ISC port does not forward the packets to any of the
DT trunks; the packet is sent only over the non-DT ports. The one exception is if the DT trunk on the
peer aggregation device is down, then traffic received over the ISC is forwarded to the
corresponding DT trunk.
About configuring peer-keepalive links 165