Hi,
we don't have a a good problem description for performance issues, here are some questions to help you get started:
- Define "performance", how is it measured? Is it raw ip throughput, icmp round trip time, or application performance?
- "Slow" is a relative word, slow compared to what? What's to be expected?
- Scope of the problem: network wide, specific ip flows, or specific application within an ip flow?
- When is it a problem? When is it not a problem? How long does it last? Any identifiable trigger?
Look for generic system resource problems
Here are some of the common places where you would want to look for typical system resource issues that may result in packet drops. Here are some best practices when using these commands for troubleshooting:
clear counters to establish a good baseline- If the problem is unpredictable, use an EEM script to capture the information periodically
- Remember counters are only useful when they are looked at as a delta, so almost always take multiple snapshots of these outputs
- ALWAYS enable
terminal exec prompt timestampt to give a time reference for the show command output
show proc cpu
Things to look for:
- Overall sustained high cpu
- Is high cpu caused by process or interrupt level? if process level, which process?
- Unusually high level of process switched traffic manifested in high cpu in "IP Input" process.
- High interrupt level CPU is indicative of high traffic volume
show interface
Things to look for:
- Input/output drops
- If drops from input queue, that implies process switched traffic, use next command
show interface stats
Things to look for:
- Which interface is doing most of the process switching
- What's the traffic direction
Once you have determined that there is heavy process switching going on, the best way to isolate which feature is causing the problem would be to try to remove one L3 feature at a time from the interface and re-test
show ip traffic
Things to look for:
- Protocol drops for the specific protocol in question (this is mostly applicable for to-the-box traffic)
Make sure the CEF is enabled, it would get better the performance.
Also take a look to the following document regarding fragmentation as well:
- http://www.cisco.com/c/en/us/support/docs/ip/generic-routing-encapsulation-gre/25885-pmtud-ipfrag.html
Please don't forget to rate and mark as correct the helpful Post!
David Castro,
Regards,
