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Sorry, Another way is through GRE tunnel, but you need router instead of FW. The doc I gave was for GRE. Following one is for ASA OSPF configuration.http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00804acfea....
IPsec VPN tunnel doesn't support multicast. So EIGRP appears not fit. OSPF has one mode p2p no-broadcast can work via VPN on ASA. see doc. http://www.cisco.com/en/US/tech/tk583/tk372/technologies_configuration_example09186a00800a43f6.shtml
From 8.0 on ASA it supports EIGRP. I've set up and live in my network. it works fine so far.http://www.cisco.com/en/US/docs/security/asa/asa80/configuration/guide/ip.html
