Troubleshooting guide

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ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Chapter 12 Troubleshooting Layer 2 Interfaces
Troubleshooting Trunk Port Problems
If you determine that IRB is configured incorrectly, refer to the “Configuring Bridging” chapter in the
Layer 3 Switching Feature and Configuration Guide.
Troubleshooting Trunk Port Problems
The switch router software provides several show commands that can be used for troubleshooting.
Troubleshooting Trunk Port Problems
To troubleshoot trunk port problems, use the following command:
Troubleshooting Fast EtherChannel Problems
This section describes troubleshooting Fast EtherChannel problems and includes the following:
• Bridging Over Fast EtherChannel Overview, page 12-16
• Troubleshooting Bridging Over Fast EtherChannel, page 12-17
Bridging Over Fast EtherChannel Overview
Ether Channel is a trunking technology that groups together multiple full-duplex 802.3 Ethernet
interfaces to provide fault-tolerant, high-speed links between switches, routers, and servers.
EtherChannel is a logical aggregation of multiple Ethernet interfaces. EtherChannel forms a single
higher bandwidth routing or bridging endpoint. EtherChannel is designed primarily for host-to-switch
connectivity or Inter-Switch Link (ISL) switch-to-switch connectivity (for example, connectivity to a
Catalyst 5500 switch).
In summary, EtherChannel provides the following benefits:
• Logical aggregation of bandwidth
• Load balancing
• Fault tolerance
The EtherChannel interface (consisting of up to four Ethernet interfaces) is treated as a single interface,
which is called a port channel. You must configure EtherChannel on the EtherChannel interface rather
than on the individual member Ethernet interfaces. You create the EtherChannel interface by using the
interface port-channel interface configuration command. The switch router supports up to 64 port
channels.
EtherChannel connections are fully compatible with Cisco IOS VLAN and routing technologies. The
ISL VLAN trunking protocol can carry multiple VLANs across an EtherChannel, and routers attached
to EtherChannel links can provide full multiprotocol routing with support for host standby using Host
Standby Router Protocol (HSRP).
Command Purpose
show epc patricia interface {fastethernet |
gigabitethernet} slot/subslot/port vlan vlan detail
Displays the patricia tree information for the
specified VLAN (for each VLAN on trunk).