Specifications

Switching 8-55
Software Release 2.7.3
C613-03098-00 REV A
The Relationship between Spanning Trees and
Trunks
If multiple links are trunked together, either manually or by using an automatic
process such as LACP, the spanning tree application is notified and considers
the links as a single logical path. Consequently, the spanning tree broadcast
messages (BPDUs) only traverse the master trunk path.
Whether trunking offers a better solution depends on the individual network
configuration. Users are recommended to consider both alternatives and select
the option (Trunking or MSTP) that best meets the requirements of the
particular network.
Hardware Packet Filters
The switch hardware can be configured to discard, forward, mirror, or change
the priority of packets matching specified criteria at wirespeed. For Rapier i
Series switches, filters can also be configured to provide a range of Quality of
Service (QoS) controls, including changing the DSCP byte, and actions can be
specified for packets that match the ingress and egress ports of the filter (if set),
but do not match the filter’s other parameters.
Two sets of commands are available, one based on the Packet Classifier (see
Chapter 34, Generic Packet Classifier), and one based on Layer 3 filter matches
and entries. These two filter types cannot be used together.
When Internet Group Management Protocol (IGMP) snooping is enabled, it
uses a hardware filter, which reduces the number of available filters. IGMP
snooping is enabled by default, but can be disabled to make its filter available
by using the command:
disable igmpsnooping
When IGMP snooping is disabled, multicast packets flood the VLAN.
IGMP snooping cannot be enabled unless a filter is available. To enable IGMP
snooping, use the command:
enable igmpsnooping
For more information, see “IGMP Snooping” on page 24-26 of Chapter 24, IP
Multicasting.
Classifier-Based Packet Filters
The switch hardware can be configured through entries in the Packet Classifier
to copy, drop, forward, and associate QoS attributes to Layer 3 packets that
match the criteria set using the classifier (see Chapter 35, Quality of Service
(QoS) and Chapter 34, Generic Packet Classifier).
Every packet passing through the switch is matched against a series of
classification tables by the Packet Classifier. Packets can be classified according
to:
• Packet type