A 2900 series router has 3 interfaces.
gi0/0 connects to the internet.
gi0/1 connects to the inside network
gi0/2 connects to the ASA firewalls
The 2900 router routes out to the internet in front of the ASAs. It also is a voice gateway, hence the gi0/1 on the inside network. It also does IPSEC VPN using VTI tunnels (there's also a backup DSL on dialer 0).
I have 2 VRFs, the global and VRF2 (not really the real name) VRF2 which is configured onto gi0/2.
The way I have routing is inside network route to the inside of the ASA. ASA default route to 2900 gi0/2. VRF2 default route to the global routing table which is upstream of gi0/0.
I want the interface of gi0/1 to have a default route of the ASAs so SIP traffic goes that way. But I don't want to break SIP or anything else. So, I'm thinking of placing the interface gi0/0 into VRF2 so that only internet traffic is separated from everything else. However I still need the VTI VPNs to come in on gi0/0.
So:
Will the VTI's still work if I place gi0/0 in a different VRF but have the "interface tunnel x" in the global route table?
Another reason I am thinking of doing it this way is I think I read a while ago that I could break the voice services of the 2900 if I put gi0/1 into a VRF.
You can defo source VTI VPNs off VRF interfaces.
Front VRF is a common design in DMVPN deployments
https://supportforums.cisco.com/document/51931/vrf-aware-ipsec-cheat-sheet
http://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/Aug2013/CVD-VPNWANDesignGuide-AUG13.pdf