What's the IOS version that include IPsec feature
on the router 2600 and 2500?
Thanks in advance.
Every IOS version since 12.0 (or thereabouts) has IPsec provided you get the feature set with it.
When you're on the IOS download page (http://www.cisco.com/kobayashi/sw-center/sw-ios.shtml) select the router and version you want then get the "IPSec DES" or "IPsec 3DES" feature set, it'll have IPSec in it.
The IOS filename will have a k8 (DES) or k9 (3DES) in it if you're not sure.
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: