[strongSwan] cannot respond to IPsec SA request because no connection is known

[Daniel Mentz]

On 07/09/2011 10:44 PM, Micah Anderson wrote:
> For some reason that i do not understand, I'm getting:
>
> Jul  9 22:37:41 kestrel pluto[3901]: "l2tp-psk"[2] 208.54.45.249:58920 #1: cannot respond to IPsec SA request because no connection is known for 198.252.153.38:4500[198.252.153.38]:17/1701...208.54.45.249:58920[26.164.21.104]:17/%any==={26.164.21.104/32}

>
> conn l2tp-psk
>    authby=secret
>    pfs=no
>    compress=no
>    rekey=no
>    keyexchange=ikev1
>    keyingtries=3
>    type=transport
>    leftprotoport=17/1701
>    right=%any
>    rightprotoport=17/%any
>    auto=add

You specified transport mode in your config, right? However, it looks 
like your peer wants to setup a connection using tunnel mode:
It says

"208.54.45.249:58920[26.164.21.104]:17/%any==={26.164.21.104/32}"

which means that your peer is 208.54.45.249, and this peer wants to 
secure traffic for the subnet 26.164.21.104/32. This won't work in 
transport mode because in this mode both peers only secure their own 
traffic.
-Daniel