Configuring Site To Site IPSec VPN Tunnel Between Cisco Routers
ISAKMP is a protocol, which is actually does the negotiation between 2 hosts. ISAKMP Security Association is we call as the Phase 1 and IPSec Security Association is we call as phase 2.
ISAKMP - Internet Security Association Key Management Protocol.
Our example setup is between two branches of a small company, connected via ISP router (R2). Both are using static IPs.
Pre-share - Use Pre-shared key as the authentication method
Group 5 - Diffie-Hellman group to be used.
To configure IPSec we need to setup the following in order:
Create extended ACL
Create IPSec Transform
Create Crypto Map
Apply crypto map to the public interface
We simulated this IPSEC site to site VPN tunnel on GNS3.
verification commands.
show crypto isakmp sa
show crypto ipsec sa