I'm not sure i understand. A L3 etherchannel on the router side but connecting to what on the firewall side ie. each firewall has one outside interface so the active firewall will only have one interface so what are you going to etherchannel to from the router ?
Apologies if i am misunderstanding but it sounds like you are trying to run an etherchannel from the router to both ASAs and this wouldn't work. It might work if the firewalls were clustered but i couldn't say as i have no experience with that.
I am not sure why you cannot simply add another switch for redundancy ie. you connect easch router interface to a different switch. The active ASA connects to one switch and the standby to the other switch. The switches are interconnected as i described in my previous post.
Then the failure of one switch still means you have connectivity from the ASA firewalls to the router although obviously losing a switch would mean a failover of the firewalls.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...