Interface Settings; Ping End Device; Switch Performance; Speed, Duplex, And Autonegotiation - Cisco Catalyst Micro Series Hardware Installation Manual

Troubleshooting
• Verify the cable type. Many legacy powered devices, including older Cisco IP phones and access points

Interface Settings

Verify that the interface is not disabled or powered off. If an interface is manually shut down on either side
of the link, it does not come up until you reenable the interface. Use the show interfaces privileged EXEC
command to see if the interface is error-disabled, disabled, or shutdown on either side of the connection. If
needed, reenable the interface.

Ping End Device

Ping from the directly connected switch first, and then work your way back port by port, interface by interface,
trunk by trunk, until you find the source of the connectivity issue. Make sure that each switch can identify
the end device MAC address in its Content-Addressable Memory (CAM) table.

Switch Performance

Speed, Duplex, and Autonegotiation

If the port statistics show a large amount of alignment errors, frame check sequence (FCS), or late-collisions
errors, this might mean a speed or duplex mismatch.
A common issue with speed and duplex occurs when duplex and speed settings are mismatched between two
switches, between a switch and a router, or between the switch and a workstation or server. Mismatches can
happen when manually setting the speed and duplex or from autonegotiation issues between the two devices.
To maximize switch performance and to ensure a link, follow one of these guidelines when changing the
duplex or the speed settings.
• Let both ports autonegotiate both speed and duplex.
• Manually set the speed and duplex parameters for the interfaces on both ends of the connection.
• If a remote device does not autonegotiate, use the same duplex settings on the two ports. The speed

Autonegotiation and Network Interface Cards

Problems sometimes occur between the switch and third-party network interface cards (NICs). By default,
the switch ports and interfaces autonegotiate. Laptops or other devices are commonly set to autonegotiate,
yet sometimes autonegotiation issues occur.
that do not fully support IEEE 802.3af, might not support PoE when connected to the switch by a crossover
cable. Replace the crossover cable with a straight-through cable.
Caution Noncompliant cabling or powered devices can cause a PoE port fault. Use only
standard-compliant cabling to connect Cisco prestandard IP Phones and wireless
access points or IEEE 802.3af-compliant devices. You must remove any cable
or device that causes a PoE fault.
parameter adjusts itself even if the connected port does not autonegotiate.
Cisco Catalyst Micro Series Switch Hardware Installation Guide
Interface Settings
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