As an experienced Cisco network engineer, you have often saved yourself from being locked out of a router when you make a change with a “reload in x” command. This handy command reboots most Cisco devices (routers, switches, firewalls) in the x number of minutes that you had specified. Thus, if you made a change that killed your connection to it, then you just have to wait until the time expires and the device reboots back up with the last saved configuration, allowing you to reconnect and remove your palm from your forehead.
Recently, I have been working to upgrade Cisco network devices, mainly routers and switches, for a client. A recent network audit identified fragmentation in the IOSes and also security advisories. As a result, all the routers and switches required upgrades and it was a good opportunity for the client to standardize the IOSes for the different type of network devices in the environment.
Two years ago Cisco introduced the Catalyst 9000 series switches as the next generation of campus switches. Every Catalyst switch family had an equivalent 9K to replace it; the 3800s were replaced with the 9300, the 4500s were replaced with the 9500, and the long standing 6500 chassis switches were replaced with the 9400. Cisco was consolidating all Catalyst switches into the 9000 series, well all but one. It seemed, at the time, that the wildly successful Catalyst 2000 series switch was spared from the chopping block as there was no comparable 9K. Enter the 9200!
IOS XE supported switches such as the 3850 and 3650 support two modes, Bundle mode and Install mode. New switches, by default, are shipped with install mode. If you never paid attention during an IOS XE upgrade on a switch you may have just copy the IOS XE image to flash and set the system boot variable to boot from the new IOS using the command below:
Have you ever found yourself in a position where throughput between devices, either local or across a WAN, seemed lower than expected? You may start by checking the configuration and logs on the network devices along the path, hoping to identify something out of the ordinary or unusual. Often a smoking gun isn’t immediately identifiable which then requires a coordinated approach to troubleshooting and narrowing down the potential causes. This write-up aims to provide some of the practices and tools I’ve used in similar situations.
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