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ZT8101 User’s Manual 27
Switch Management and Operating Concepts
Each port on the switch is a unique collision domain, and the switch filters (discards) packets
whose destination lies on the same port as where it originated. This keeps local packets from
disrupting communications on other parts of the network.
The switch does some filtering automatically:
• Dynamic filtering—The switch automatic learns and ages MAC addresses and their location
on the network. Filtering occurs to keep local traffic confined to its segment.
• Filtering done by the Spanning Tree Protocol—STP filters packets based on topology,
ensuring that signal loops don't occur.
• Filtering done for VLAN integrity—The switch filters packets from a member of a VLAN
(VLAN 2, for example) destined for a device on another VLAN (VLAN 3).
You can also manually configure the switch to drop packets from specified MAC and IP addresses.
Whenever a switch encounters a packet originating from, or destined to, a MAC address or an IP
address entered into the filter table, the switch discards the packet.
MAC Address Filtering
When filtering by MAC address, you have two options:
• Static—This option allows you to specify which port handles the packets from the specified
MAC address.
• BlackHole—This option allows you to have the switch drop the packets from, or to, a
specified MAC address.
IP Address Filtering
When filtering by IP address, you have three options. You can have the switch drop the packet
based on where the IP address appears:
• In the source
• In the destination
• In both the source and destination
The table can contain 32 entries, and two table entries are needed to configure a bi-direction filter.
Port Mirroring
Port mirroring allows the traffic on a particular port to be monitored by sending copies of the
packets to a target port. You can then attach a logic analyzer or a RMON probe to the target port
and study the traffic crossing the source port in a completely unobtrusive manner. You can
configure only one port to be a target port, but you can select multiple ports to be mirrored to this
target port. For optimum performance, you should mirror three or fewer ports at any given time.
You can select which traffic is mirrored. For a given mirrored port (or source port), you can select
to mirror only incoming traffic, only outgoing traffic, or both.
When mirroring ports, remember the following:
• The source port cannot be the target port.