IPsec tunnel not being up between AR router and another vendor router
Issue Description
Handling Process

2) We checked the “ display ike error-info”, error reason is phase2 proposal , PFS mismatch or flow mismatch but I checked all parameters are OK and matched

3) i checked the phase2 parameters on both sides , it is matched .
4) in other vendor device , interface tunnel 1 is by default on GRE mode ,after changing it from GRE mode to IPsec mode ,issue resolved
RouterB(config)#interface tunnel 1
RouterB(config-if)#tunnel mode ipsec ipv4
Root Cause
Solution
RouterB(config)#interface tunnel 1
RouterB(config-if)#tunnel mode ipsec ipv4
Reference from our documentation