To avoid
miscon?¬?guration and to troubleshoot ef?¬?ciently, you should understand the mechanism
used by the Layer 3 forwarding device. If you are sure that the equipment is properly
con?¬?gured, yet hardware switching is not taking place, then a software bug or hardware
malfunction may be the cause.
Table 2-15 DTP Mode Examples
Configuration Parameter Description
Dynamic Auto Creates the trunk link based on the DTP request from the
neighboring switch. Dynamic Auto does not initiate the
negotiation process; therefore, two switches set to Dynamic
Auto do not form a trunk link.
Dynamic Desirable Communicates to the neighboring switch via DTP that the
interface would like to become a trunk if the neighboring
switch interface is able to.
82 Chapter 2: Medium-Sized Switched Network Construction
Another type of miscon?¬?guration that affects inter-VLAN routing is miscon?¬?guration on
end-user devices such as PCs. A common situation is a miscon?¬?gured PC default gateway.
Too many PCs having the same default gateway can cause high CPU utilization on the
gateway, which affects the forwarding rate.
Troubleshooting VTP
Another important aspect of troubleshooting is the ability to identify and resolve VTP
issues, assuming port connectivity and VLAN problems have been identi?¬?ed and resolved.
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