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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 10 Configuring the Switch Ports
Configuring UniDirectional Link Detection
Configuring UniDirectional Link Detection
UniDirectional Link Detection (UDLD) is a Layer 2 protocol that detects and shuts down unidirectional links.
You can configure UDLD on the entire switch or on an individual port. Use the udld reset command to
reset all ports that have been shut down by UDLD.
Beginning in privileged EXEC mode, follow these steps to configure UDLD on a switch:
Understanding SPAN
You can analyze network traffic passing through ports or VLANs by using SPAN to send a copy of the
traffic to another port on the switch that has been connected to a SwitchProbe device or other Remote
Monitoring (RMON) probe. SPAN mirrors received or sent (or both) traffic on one or more source ports
to a destination port for analysis.
For example, in Figure 10-4, all traffic on FastEthernet port 5 (the source port) is mirrored to
FastEthernet port 10 (the destination port). A network analyzer on port 10 receives all network traffic
from port 5 without being physically attached to port 5.
Figure 10-4 Example SPAN Configuration
Only traffic that enters or leaves source ports can be monitored by using SPAN.
This release supports only local SPAN, which means the source and destination interfaces must be on
the same switch.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
udld enable Enable UDLD on all switch ports.
Use the udld interface configuration command to enable UDLD on
a specific port.
Step 3
end Return to privileged EXEC mode.
Step 4
show running-config Verify the entry by displaying the running configuration.
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Port 5 traffic mirrored
on Port 10
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Network analyzer
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