i have 2 sites in redundancy. For this i must use bgp v4. I know asa doesn't handle bgp v4 but i want to know if a router 26xx or 28xx with a security ios can make BGP?
Or i must buy a router for bgp and a firewal?
A router with security IOS can certainly do BGP. Whether that provides sufficient security implementation and would be equivalent to having a firewall is a question that can only be answered by someone who knows more about your network and your requirements than we do.