Datacenter Notes

For CISCO Devices

Upgrading IOS

This is a small step-by-step guide on updating IOS annotated from a script(1) transcript I took from a while back. In my case I'm upgrading IOS 12.1(20)EA1a to IOS 12.1(22)EA14, the latter of which is the last version supporting the Catalyst 2950 series.

And there you go!

If something goes wrong at this point (i.e. image got corrupted somehow and does not boot) you can transfer the old image using XMODEM over the serial line. This is a slow process though. See the respective handbook from CISCO on how to do that.

Also a consideration: Update the Sticker on the rear to match the currently installed IOS. My sticker was still from the factory installed IOS 12.1(6)EA2a even though it was upgraded to the aforementioned IOS 12.1(20)EA1a at some point.

It *really* helps when you can look at the sticker in the back and know what the switch is running, there is nothing more annoying than thinking that you have to upgrade IOS, allocate time for it and then realize that it is already up to date once you are hooked up to it.

Interface based Rate limiting

You can accomplish bandwidth limiting on a per-interface basis as follows

Switch$ execute
Switch# configure terminal
Switch(config)# interface FastEthernet 0/n
Switch(config-if)# srr-queue bandwidth limit percent

Where n is the interface on module 0 and percent is the percentage you want to block on the interface.

The formula to calculate the percentage is as follows:

Where Bwant is the maximum bandwidth you want to allow on the interface and Bmax is the maximum theoretical bandwidth of the interface.