Configuring Unidirectional Link Detection; Understanding Span - Cisco Catalyst 2950 Software Manual

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:
Command
Step 1
configure terminal
Step 2
udld enable
Step 3
end
Step 4 show running-config

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
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
1
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.
Catalyst 2950 Desktop Switch Software Configuration Guide
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Figure 10-4, all traffic on FastEthernet port 5 (the source port) is mirrored to
1 2 3 4 5 6 7 8 9 10 11 12
6 7
5 8
4 9
3
2
Network analyzer
Purpose
Enter global configuration mode.
Enable UDLD on all switch ports.
Use the udld interface configuration command to enable UDLD on
a specific port.
Return to privileged EXEC mode.
Verify the entry by displaying the running configuration.
Port 5 traffic mirrored
on Port 10
11
12
10
Chapter 10 Configuring the Switch Ports
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