iproute nexthop not working - defining multiple default gateways

Question

I have several point to point connections and I’d like to use all of them as default gateways. I saw this link which explains how to do this using load balancing by calling ip route with a next hop definer, but when I run the command it says:

RTNETLINK: invalid argument.

I know about bonding, but I cannot use bonding in my scenario because it cannot be easily done for PPP connections.

Here is the command:

ip route add default scope global next hop via $P1 dev $IF1 weight 1 nexthop via $P2 dev $IF2 weight 1

Where $P1 is gateway address for ppp1 and $IF1 is pp1 and so forth. Here is the link.

my kernel is 2.6 and the document seems to indicate kernel version 2.2/2.4 could that be the reason?