2.5 Given a scenario, troubleshoot common router and switch problems.

2.5 Given a scenario, troubleshoot common router and switch problems.
 * Switching loop
 * Bad cables/improper cable types
 * Port configuration
 * VLAN assignment
 * Mismatched MTU/MUT black hole
 * Power failure
 * Bad/missing routes
 * Bad modules (SFPs, GBICs)
 * Wrong subnet mask
 * Wrong gateway
 * Duplicate IP address
 * Wrong DNS