I am trying to diable aggressive mode, for security reasons. I have a Cisco 3825 running c3825-advsecurityk9-mz.124-24.T2.bin. When I disable aggressive mode with ROUTER(config)#crypto isakmp aggressive-mode disable , I am unable to connect. The syslog message displayed is > %CRYPTO-5-IKMP_AG_MODE_DISABLED: Unable to initiate or respond to Aggressive Mode while disabled and the client error is Reason 412: The remote peer is no longer responding.
I am using the Cisco VPN client to connect, so there isn't a way to disable aggressive mode. But from what I just finished reading.. The only way to use main mode is use certificates, if you use a PSK(which I do for the group) then aggressive mode has to be enabled.
