behind the firewall. A & B has their own Internet route. Site C has one firewall, one 3750 switch and two T-1 links. one T1 point to site A and other to site B. Site C will have two VLANs and each VLAN will belong to site A and other to site B VLAN.  My boss wanted site A & B to talk to each other via the trunk link between them. If the trunk link between A&B failed, traffic should routed to A&B tunnel.  Site A has 3 Cisco 3750s and 3 for site B.He wanted each switch to have  physical connection to the firewall in case one switch goes down the others should resume normal functions.I plan on layer 3 switching but each switch must physically connect to ASA5520 got me researching various designs.

My questions are:

Can a tracking function work on ASA5520 tunnel between site A&B?

Should I implemented a separate layer 3 switching for site A&B? or put them in one L#3 and one VTP domain or separate them?

also, adding EIGRP as routing protocol will help?

Also ASA5520 failover-should I go for active/standby or VRRP or GLBP?

Thank you very much for reading this post and your best possible advise.

Thanks,

Eric