Dip Dive into Nexus troubleshooting plus cat4500 tshoot & Cat3850 high cpu .
•Work towards turning initial problem description into platform specific problem description.
•Define “broken” and /or “not working”
•Understand how whatever is “not working” should be working
•Determine possible triggers, patterns, timestamps etc.
•Understand the topology when relevant
“Initial” problem description: We’re having protocol <x> changing states intermittently
“platform specific” / desired problem description: OSPF is flapping , only b/t these two specific links, not an issue on any other OSPF interfaces, and it looks as if box <x> stops transmitting hello packets from the CPU whenever it’s being polled by this SNMP device every 5 minutes.
Topic:
Nexus troubleshooting part 1- 7
Cat 4500 troubleshooting part 1-3
Cat 3850 high cpu
• Contrary to popular belief…..
TAC esc, BU esc, DEs, TMEs, cs-nexus7000 do not have a magic wand to answer vague scenarios such as previous “initial” problem description.
•Hence the importance to get to a platform specific / component problem description.
•DEs that monitor the alias are not typically “network” troubleshooters, but are “feature” troubleshooters. So “escalating to DE/BU” is not a productive step unless the necessary info is gathered prior.
•Show techs are ‘not’ meant to simply be gathered and then passed to your direct escalation or alias.
It is ok “not to know” what you’re looking for in every show tech.
++++++ADDED++++++++
Good idea of the capabilities of Ciscoswitches/routers in terms of various troubleshooting tools, especiallypacket capture tools. Ability to choose the right tool totroubleshoot, which helps for timelyresolution of the problem.
Importance
The most important function of packet capture is network detection. The process of packet capture is similar in essence to telephone wiretapping, as it detects everything going through the computer networks. The main function of it is to monitor network performance and troubleshoot any problems which may arise. Sniffers can also capture data from diverse parts of the network using a monitoring port. This type of interface intercepts data from different points and sends them to the network administrator, to be decoded and analysed.
Topics Covered :
Flexible NetFlow (FnF)
Embedded Packet Capture Tools
SPAN / RSPAN / ERSPAN
Ethanalyzer and NetDR
VACL and ACL Capture
ELAM
Putting It All Together
Summary and Take Away
