what is the difference between the ios version and bootstrap version?

[huangzhy]

what is the difference between these two versions?Do they need to be the same version in order for best performance?And if i upgrade the main ios version,do i need to upgrade bootstrap version too? If i don't ,is there any problem?

[rsissons]

The boot code is a cut down version of IOS which is only used to load in a full IOS version.

The only reason to upgrade the boot code is if you upgrade the router with new hardware interfaces, over which you may wish to download a full IOS using the boot code, if the existing boot code does not have support for them.