Trying to figure out if its possible to setup multiple site to site connections to one location. Situation is this, there are 12 offices, one of which is the HQ office, I'm wondering if its possible with a large enough Cisco router to create a site to site tunnel from each location to HQ, so basically 11 tunnels all ending at the HQ router. The reason for setting this up is that each location needs to have the ability to communicate with the HQ server in a secure fashion. Is this setup possible? If so I was thinking I would use GRE and IPSec with IKE authentication being done using a pre-shared key (side question: for this does IKE use the same key for each tunnel or different, i'm thinking different but i could be wrong). I'm also thinking of implementing QoS for each tunnel to ensure one tunnel doesn't eat up to much bandwidth. Is this the best way of doing this, or can ya'll think of something better. I'm also wondering if its possible with this setup for the other sites to communicate with one another if necessary.
Each site would need to be on a non overlapping subnet to every other site to be able to do this without NAT.
The size of the router would be dependant on the VPN bandwidth that you required rather than the number of VPNs.
You might also look at the Cisco ASA firewalls instead of using routers.