Cisco CATALYST 3920 24 PORT TOKEN RING SWITCH Техническое Руководство
Introduction to the Catalyst 3920 1-3
Filtering
Many bridged networks today employ filtering to reduce broadcast traffic, block protocols, and
provide simple security. The Catalyst 3920 provides filtering capabilities for the same purpose. You
can filter frames based on the following:
provide simple security. The Catalyst 3920 provides filtering capabilities for the same purpose. You
can filter frames based on the following:
•
MAC address (source address, destination address)
•
Protocol (destination service access point [DSAP]/Subnetwork Access Protocol [SNAP] Type)
MAC address filters and broadcast filters can be applied only at input ports. DSAP and SNAP filters
can be applied at input ports and output ports.
can be applied at input ports and output ports.
Notification of Port Errors and Beacon Situations
The Catalyst 3920 is notified when a serious error, such as signal loss, is detected. The Token Ring
port is then instructed to discard all frames in the output queue and to reject new frames.
port is then instructed to discard all frames in the output queue and to reject new frames.
The Catalyst 3920 is also notified when a Token Ring beacon state is detected on the ring and when
it disappears. If the beacon state remains for more than a specified amount of time, the port is
instructed to discard all frames in the output queue and to reject new frames. When the beacon state
disappears, the port is instructed to once again accept frames.
it disappears. If the beacon state remains for more than a specified amount of time, the port is
instructed to discard all frames in the output queue and to reject new frames. When the beacon state
disappears, the port is instructed to once again accept frames.
Cisco Discovery Protocol Support
The CDP support allows the Catalyst 3920 to establish communication with other models of Cisco
equipment. CDP support is provided as part of the Cisco IOS software that runs on many types of
Cisco equipment.
equipment. CDP support is provided as part of the Cisco IOS software that runs on many types of
Cisco equipment.
CDP is a media- and protocol-independent protocol that is intended to be run on Cisco-manufactured
equipment including routers, bridges, access servers, and switches. With CDP, Cisco’s network
management applications and Cisco devices can learn the device type and the SNMP agent address
of neighboring devices. This enables applications to send SNMP queries to neighboring devices.
equipment including routers, bridges, access servers, and switches. With CDP, Cisco’s network
management applications and Cisco devices can learn the device type and the SNMP agent address
of neighboring devices. This enables applications to send SNMP queries to neighboring devices.
CDP runs on various media that support the SNAP, including LAN, Frame Relay, and Asynchronous
Transfer Mode (ATM) media. CDP runs over the data link layer only. Therefore, two systems that
support different network-layer protocols can learn about each other.
Transfer Mode (ATM) media. CDP runs over the data link layer only. Therefore, two systems that
support different network-layer protocols can learn about each other.
Each device configured for CDP sends periodic messages to a multicast address. Each device
advertises at least one address at which it can receive SNMP messages. The advertisements also
contain time-to-live, or holdtime, information, which indicates the length of time a receiving device
should hold CDP information before discarding it.
advertises at least one address at which it can receive SNMP messages. The advertisements also
contain time-to-live, or holdtime, information, which indicates the length of time a receiving device
should hold CDP information before discarding it.
VLANs
The VLAN feature allows you to partition a Catalyst 3920 into multiple VLANs by assigning
multiple ports within a single switch or a stacked configuration of switches to the same logical ring
number. For each VLAN that you establish, you can configure separate IP, SNMP, and spanning-tree
parameters. You can also configure the Catalyst 3920 to bridge traffic between the logical rings of a
switch or switch stack.
multiple ports within a single switch or a stacked configuration of switches to the same logical ring
number. For each VLAN that you establish, you can configure separate IP, SNMP, and spanning-tree
parameters. You can also configure the Catalyst 3920 to bridge traffic between the logical rings of a
switch or switch stack.