ipsec tunnel site to site with AVAYA SCN

[PIDDLAW]

We had an issue where our AVAYA ipoffice SCN would not come up over our IPSEC tunnel between a 100d and a 60cWIFI. All other triaffice from computer to server etc.. was perfect on the ipsec vpn. We went round and round with avaya and fortigate support trying to fix it. I changed ONE THING and it worked. I have not changed it back to see if that was the actual cause. here is what i changed. the 60w at the remote site is acting as a dhcp server, giving out addresses 192.168.8.100-192.168.8.210 We had originally setup the IPOFFICE unit to an IP of 192.168.8.220. that never did work correctly. I then changed the ip address of the IPOFFICE unit to 192.168.8.210. and like magic it worked. I am wondering, did things not route correctly (all packets) because the ip of the IPOFFICE was outside of the fortigates " scope" ? We could see them talking before but never relaiably and never over port 50795.(the port to establish the scn) any ideas as to if this was the case or not would be welcome. sorry I am new to the fortigate product line. Dave