[strongSwan] strongswan one tunnel multiple hosts question

[lux-integ]

Greetings,
I am setting-up strongswan 
( I have compiled and installed version-5.2.0 ).
And  I have the following setup:-
eternalHost|gateway|subnetA|internalRouter|subnetB|targethost
I want to   tunnel stuff from externalHost to targetHost

For the internal part I have ipsec.conf  with entries ike the folloing:-


ca=crlurl,aiaurl etc
conn %default

conn gateway-internalrouter
  leftid=hostname.example.com
  rightid=hostnameinternalRouter.example.com
  leftsubnet=subnetA,subnetB

I also have a connection subnetA-subnetB
conn subnetA-subnetB
  leftsubnet=subnetA
  rightsubnet=subnetB

-------------
I hope the above   describes a tunnel from the gateway to  subnetB. 
I am intrigued by the multiple subnet settings  and would like to know    if 
one can reach targethost from within the ipsec.conf on  gateway..  Accordingly  
I have the following: QUESTION:
Can one define a connection in ipsec.conf  FOR gateway1 )  that reads 
something like
conn   internalRouter-targethost
  leftid=internalRouter.example.com
  rightid=targethost.example.com

and so on ?

and if one could how would it be started   etc etc ?

Thanks in advance
sincerely
luxInteg