IPsec VPN using linux kernel 2.6 I'm trying to implement mip6d on my laptop using debian9 but I have to downgrade to an older kernel linux (linux 2.6) to install de racoon2 (software that allow exchanges and installs of security parameters). When I download this version and try to do the make command nothing is going on because I think that the problem is related to the gcc that my debian9 is using to do the make command. If any one did the same thing that I am trying to do (downgrade to kernel linux 2.6), let me know how I can fix this.

For dealing with IPsec in Linux, the advised way is using Strongswan.

Strongswan has well supported Debian packages nowadays; there are also a lot of advance in protocols supported and security bugs fixed, so going backwards for 2.6 is frowned upon. (And that supposing you manage to make the rest of the components of your system work properly with a 2.6 kernel).

I advise not trying to follow old tutorials, contrary to the past, for instance nowadays in Debian 9, you pretty manage to setup an IPsec VPN + IKEv2 without having to resort to compile any component.

For an example, see Setting up a secure VPN with strongSwan on debian

PS. The compiled part in that link is dnsproxy, which is not entirely relevant to the IPsec discussion per se, it is more a setup for fighting DNS leaking, and Debian also has a package for it.