[plug] IPSec / L2TP and VPNs

[Steve Baker]

Hi Pluggers,

I want to set up a VPN between our main office and another site.  The 
two office networks have private IPs (192.168.100.xx and 
192.168.110.xxx) and the gateways/firewalls have public IPs.  Eventually 
there will be more site offices that will need to communicate back to 
home base.

Apparently I can set up an encrypted VPN purely with IPSec - can anyone 
confirm that this is the case?  Or do I need to use L2TP also?  I've 
been reading some papers about this stuff, and it seems that I just need 
to configure the kernel for IPSec, write up some relatively simple 
config files, and it 'just works'.  Most of the information I've found 
is a year or so old, so I'm not sure if it's still current.  There are 
many references to FreeS/WAN (defunct) and OpenS/WAN (not) but I'm not 
sure if I need to use the openswan bits or just straight IPSec. Suggestions?

I'm also not sure about what sort of entries I need to add to the 
routing tables, if any.  Does the kernel 'just know' how to route stuff 
through the VPN tunnel?  Or do I need to add a routing entry?

Pointers to good quality and fairly thorough HOWTOs etc. would be 
appreciated.

Thanks.
Steve