This option lets you specify which local interfaces IPsec will be made
available on. Most users will want to check the Single Interface box
and leave this empty.
If you need more fine-grained control, then enter interfaces in the following
format into the box:
ipsecA=ethY ipsecB=ethZ
For example, if your machine had two interfaces and you wanted IPsec to be
available on both of them you would enter:
ipsec0=eth0 ipsec1=eth1