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C
HAPTER
 4: C
ONFIGURING
 
THE
 S
WITCH
Figure 28   Spanning Tree Tab
Forward — Spanning tree BPDU packets received on 
a port are forwarded to all other ports.
Block and Discard — Spanning tree BPDUs received 
on a port are dropped. The Switch does not forward 
BPDUs to other ports.
The Switch does not participate as a bridge node in the 
spanning tree, it can only be configured to forward or 
block spanning tree BPDUs. If the Switch is connected 
to other bridging devices, such as switches, that are 
part of the spanning tree network, set the Switch to 
"Forward." If the Switch is connected only to 
workstations, it can be set to "Block and Discard."
802.1p Prioritization
The Switch has priority queuing enabled, which means 
all packets that are received are examined to see if they 
have been priority encoded. If a packet has been priority 
encoded, then the Switch will read the priority level and 
determine whether the packet should be directed 
through the normal or high priority channel. This 
feature can be useful for example during excessive loads 
when one type of traffic may require priority over 
another. The Switch is configured to comply with 
802.1p, VLAN tagged frames.
Traffic prioritization ensures that high priority data is 
forwarded through the Switch without being delayed by 
lower priority data. It differentiates traffic into classes 
and prioritizes those classes automatically. Traffic 
prioritization uses the multiple traffic queues that are 
present in the hardware of the Switch to ensure that 
high priority traffic is forwarded on a different queue 
from lower priority traffic, and is given preference over 
that traffic. This ensures that time-sensitive traffic gets 
the highest level of service. 
The 802.1D standard specifies eight distinct levels of 
priority (0 to 7), each of which relates to a particular 
type of traffic. The priority levels and their traffic types 
are shown in the following table.
Priority Level Traffic Type
0
Best Effort
1
Background