Working on implementing Multi-WAN at our office (more about that later), in which we use a rather special routing setup, we got this error message on our IPSEC tunnels:

Quote

ipsec_setup: Starting Openswan IPsec U2.4.12/K2.6.26-2-amd64...
ipsec_setup: no default route, %defaultroute cannot cope!!!

While the reason was obvious to me (there's indeed no default route in the main routing table, this is by design), fixing the problem was not.
I tried adding options like leftnexthop=ip-address but it did not really matter; the error persisted.

After searching around Google, I came across a post with a similar error, along with an unusual solution: adding the following line solves the issue.

config setup
     interfaces="ipsec0=eth0"

The unusual about it is that I'm running a 2.6 kernel and IPSEC interfaces no longer exists. However, adding this option regardlessly overrides the implicit %defaultroute value for all interfaces.

Source: http://lists.openswan.org/pipermail/users/2005-June/005447.html