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Pre-Upgrade Verifications

Before performing a software upgrade, a competent network administrator checks the state of the chassis, including hardware integrity, peering relationships with adjacent devices, and stability of the routing tables. You do this beforehand, because there are often problems confirming stability after a software upgrade. If you have not performed a pre-upgrade check, it is impossible to know whether any problems are related to the software upgrade or whether they existed prior to the software upgrade. Commands to use and results to expect will vary by platform and by network topology.

Note

Pre-upgrade and post-upgrade verifications should be nearly identical, as it is necessary to know what normal behavior is in order to spot the abnormal behavior. Appendix B provides a checklist that you can use for both pre-upgrade and post-upgrade verification.

Filesystems and Logs

Network problems tend to be intermittent. As a result, you may not be able to directly observe device or network problems when performing a pre-upgrade verification. This situation is where logfiles come in very handy. A few searches through selected files can show recent past problems that could potentially return. Again, failure to identify a preexisting problem could result in the problem being mistakenly attributed to the software upgrade, which wastes valuable troubleshooting time.

Logfile information is commonly stored in the messages file. Additional logfiles to look at depend on syslog settings ...