IPSec tunnel between Liknux BOX and Cisco VPNC 3000 problem

I need to use differenet IPs as sources to get to different subnets as destinations but on the same IPSec tunnel, for example:
in my setkey file.

spdadd 192.168.1.12/32 10.31.215.18/32 any -P out ipsec esp/tunnel/172.16.8.10-172.18.8.10/require;

spdadd 10.31.215.18/32 192.168.1.12/32 any -P in ipsec esp/tunnel/172.18.8.10-172.16.8.10/require;


spdadd 192.168.1.11/32 10.31.10.118/32 any -P out ipsec esp/tunnel/172.16.8.10-172.18.8.10/require;

spdadd 10.31.10.118/32 192.168.1.11/32 any -P in ipsec esp/tunnel/72.18.8.10-172.16.8.10/require;

the problem is when the tunnel is up and I try to ping the first IP every thing is ok, but when I try the other one it doesn't work, so I tried to restart the tunnel, and tried to ping the second IP and it replied but when I tried the first IP it didn't work.

Does anyone knows the reason for this?

Note the other end is a cisco vpn concentrator.

Thanks in Advance

Best Regards
Ahmed Adel