Troubleshooting guide

12-14
ATM and Layer 3 Switch Router Troubleshooting Guide
OL-1969-01
Chapter 12 Troubleshooting Layer 2 Interfaces
Troubleshooting Integrated Routing and Bridging
• The protocol attributes should not be configured on the bridged interfaces when using IRB to bridge
and route a given protocol. Bridging attributes cannot be configured on the BVI.
• A bridge links several network segments into one large, flat network. To bridge a packet coming
from a routed interface among the bridged interfaces, the whole bridge group should be represented
by one interface.
• The BVI has default data-link and network-layer encapsulations. These encapsulations are the same
as on the Ethernet, except that you can configure the BVI with some encapsulations that are not
supported on a normal Ethernet interface.
Troubleshooting IRB Connections
To troubleshoot the IRB configuration, use the following commands:
Troubleshooting IRB is a combination of both Layer 2 and Layer 3 troubleshooting. Check the
following:
• Use the processes in the “Troubleshooting Layer 2 Switching” section on page 12-5.
• Use the processes in Chapter 11, “Troubleshooting Layer 3 Network Connections.”
When using these processes be aware of the following differences:
• Each physical Interface of the Bridge-Group has two MAC Addresses.
– BVI MAC Address (same as the first Member of the Bridge-Group)
– Physical MAC Address
• Packets destined to any of these MAC addresses will be considered for routing.
• The CAM must be programmed so the ingress interface can forward frames to a specific egress
interface.
• High route processor utilization is common when using IRB routing.
• Packets get switched by the route processor when the Layer3 (IP or IPX) adjacency gets invalidated
in the Layer3 CAM. This is caused by MAC address aging in the Layer 2 CAM.
Command Purpose
show interfaces bvi interface-name Displays BVI information, such as the
BVI MAC address and processing
statistics.
show interfaces irb Displays the following BVI information:
• Protocols that this bridged interface
can route to the other routed interface
if this packet is routable
• Protocols that this bridged interface
bridges
• Entries in the software MAC-address
filter