Please find IOS version for IP SEC service

[rapeepat.s]

Because want the Router 2811 support for IPsec. find the version of the Support Service as well.

Something of concern
- Memory requirements or other.
- License Base (eg IP Base image installed before the image is IP Service, will the system work?).

[Philip D'Ath]

IPSec will work fine with the base memory.

With the 2800 you have a specific image for each feature set, and you can move from one image directly to another (after a reboot).  You do need to buy the licences from Cisco for the feature set you are using.

The 2811 is pretty old now.  I doubt Cisco sell licences for these routers any more.
http://www.cisco.com/c/en/us/products/collateral/routers/2800-series-integrated-services-routers-isr/eol_c51-631228.html

You should consider moving to something modern, like a Cisco 4000 series.  A 4331 might be a good fit if you are using a 2811 now.
http://www.cisco.com/c/en/us/products/routers/4000-series-integrated-services-routers-isr/models-comparison.html

[Joseph W. Doherty]

On the 2811, IPSec "stuff" was generally included in crypto images ("k9" in image name).  I don't recall there being a separate feature license, although you did need to be approved to download a crypto image.

In other words, I recall, for a 2811, there's a non-crypto IPBase and IPServices images and crypto IPBase and IPServices images.

Depending on what you actually want to do with IPSec, besides having the crypto image, you might need a particular feature image too.