2x871-sec-k9 routers connected to different ISP.Inside ports are connected to 2950 switch.
I need to be sure that this topology will work for HSRP and DMVPN.
I've read in some forum that one can assign an ip address to any int fa0/0-3 (which I find hard to believe), so that it can become a second wan link connection.
That would be a very good solution for deploying only one router to the site.
Just to make sure if above assumption is wrong I plan to have 2x 871-sec-k9 routers.
Can I assign HSRP commands to vlan interfaces so that HSRP will work?
I understand your requirement now but unfortunately HSRP cannot be configured on a single router and basically you do not need HSRP with single router.
HSRP is for gateway load balancing and also provide default gateway redundancy for lan network. But with single router you do not need this as there will be only one gateway for your lan network.
If you want redundancy for your wan network then you can configure 2 default routes with different admin distance so that if one wan link is down your packets can move out of second wan interface. Something like this
ip route 0.0.0.0 0.0.0.0 fa0/0 90
ip route 0.0.0.0 0.0.0.0 fa0/1 100
In this way fa0/0 will always be preferred and once fa0/0 goes down traffic will start going out using fa0/1.
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