IP tunnel help please?

[Mike Dent <mike_(_at_)_dent_(_dot_)_org>]

I'd like to setup an ipv4 tunnel from my Sparc running 2.5 at home to my
linux box at work. I do this at present with linux at both ends. I'm not
too bothered about making the tunnel secure at this stage, i'd just like
to get it working. 
I've been trying to get it working with 'ipsecadm' but am rather
confused
by the SPI parameter? I used something like:-

ipsecadm ip4 -spi 1001 -src <home_backbone_addres> -dst
<work_gateway_backbone_address>

This seems to be accepted but I'm not sure where to go next? Do I need
to add a route? What name is given to the interface?

Thanks
Mike