IPIP is possible on the SRX but not in cluster
(virtual chassis mode)
Being able to setup a single or even multiple IPIP tunnels is not suffcient to
be a member of the AMPRnet IPIP mesh. See what Brian wrote:
This is a mesh network, not a star, so there is no
default route; you
need a separate tunnel route to each gateway you want to communicate with,
Marius has written a very nice script to get it working on a MikroTik router,
but most other commercial routers lack the scripting capabilities to pull this
off on their own. Someone wrote a script to use a Cisco router but it requires
a separate machine to run it.
Rob