[Openswan Users] ipsec vpn fallback

[Ming-Ching Tiew]

I have a case where I have two internet connections
( link1 a1.b1.c1.d1 and gateway a1.b1.c1.e1, and link2
a2.b2.c2.d2 and gateway a2.b2.c2.e2 ) and I want to establish 
a vpn connection to the remote office ( ip u.v.w.x and gateway 
u.v.w.y ) which is connected to the internet too.

Because internet link is unreliable, I would have setup two
internet links, and at one time, I want one IPSEC VPN 
connection to the remote office to be active. If one of the
internet link goes down, I want to establish a VPN connection
via the other surviving link.

I am using kernel 2.4.29 and openswan 2.3.1, the 'ipsec.conf' I have
included below. I could bring up ipsec on link1 ( ipsec0 ) this
way :-

       ipsec auto --up link1

This is all fine and proper, however, when the link1 fails, I 
bring down ipsec on link1 and bring up ipsec1 on link2,

      ipsec auto --down link1
      ipsec auto --up link2

The second command fail to properly establish the IKE negotiation,
it seems to do with some routing issue. If I rework the ipsec.conf,
changing interfaces="ipsec0=eth2 ipsec1=eth1" and issue commands
  
     ipsec setup restart
     ipsec auto --up link2

Then it will work. Is there a way to get this to work without changing
the ipsec.conf and restarting ipsec ?

Thank you very much for you attentions.

----------------------ipsec.conf------------------------------------
# 
version 2
## basic configuration
config setup
        interfaces="ipsec0=eth1 ipsec1=eth2"

conn link1
        keyingtries=0
        keyexchange=ike
        authby=secret
        compress=yes
        left=a1.b1.c1.d1
        leftsubnet=192.168.238.0/24
        leftnexthop=a1.b1.c1.e1 # a.b.c.d's gateway
        right=u.v.w.x
        rightsubnet=192.168.118.0/24
        rightnexthop=u.v.w.y
        auto=add
        pfs=no

conn link2
        keyingtries=0
        keyexchange=ike
        authby=secret
        compress=yes
        left=a2.b2.c2.d2
        leftsubnet=192.168.238.0/24
        leftnexthop=a2.b2.c2.e2
        right=u.v.w.x
        rightsubnet=192.168.118.0/24
        rightnexthop=u.v.w.y
        auto=add
        pfs=no