CCNP TSHOOT 6.0 - Cisco Learning Home

CCNPv6 TSHOOT
show standby vlan vlan# brief
debug standby packets
Lab 4-2 Sample Troubleshooting Flows
Troubleshooting Multilayer Switching
Note: Specific to the Catalyst 3560 and 3750 series of
switches.
Verify active and standby roles and IP addresses for a
particular VLAN for HSRP routers.
Displays real-time messages exchanged between HSRP
routers.
The figure illustrates an example of a method that you could follow to diagnose and resolve problems related to
multilayer switching.
Sample Multilayer Switching
Troubleshooting Flow
Locate failing
Layer 3 hop
Verify Layer 3 path
using traceroute
and ping
Verify
ingress
Layer 3
interface
Analyze sniffer
traces
Check
control plane
data
structures
Check
packet
switching
data
structures
© 2009 Cisco Systems, Inc. All rights reserved. TSHOOT v1.0—29
What is multilayer switching? In essence, a multilayer switch is a switch that is capable of switching Ethernet
frames based on information in the Layer 2 and Layer 3 headers. Troubleshooting Layer 2 switching was covered
in the previous lab exercise. This troubleshooting flow focuses on troubleshooting the process of switching
Ethernet frames based on Layer 3 information.
Under which kind of circumstances do you start troubleshooting the multilayer switching process?
Troubleshooting multilayer switching is just one of the steps in the bigger picture of troubleshooting network
connectivity along a Layer 3 path. After you have determined—by using tools like traceroute or ping or through
analysis of packet captures—that a particular hop in the Layer 3 path seems to be the point where packets start to
get dropped and that hop is a multilayer switch, or when you are troubleshooting performance problems and you
want to find the exact physical links on which packets travel, then start tracing and verifying the Layer 3
forwarding behavior of the multilayer switch that you suspect to be the cause of the problem.
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