I'd like to setup a Cisco 2811 router to provide site-site VPN between this router and a PIX 515 firewall. Just wanted to know which version of IOS would be best suited for the job plus 802.1Q and BGP routing features. I've configred site-site VPN before on 1800 and 800 series routers but just wanted to know whether there are additional stuff that I would need to configure on 2811 or not. Thanks.
Any Advance IP services k9 image will have support for BGP, Ipsec for L2L vpn as well as support for 802.1q trunking
You may check features here for Adv Ip services
or do a search by feature here