I wouldn't recommend a trunk If you have only two vlans. On the other hand if in the near future you're going to deploy several vlans, then I think the trunk will be necesary.
What version of ASA do you have? ASA supports etherchannel from version 8.4.2
But there are some restrictions when configure etherchannel with an ASA. For example ASA only supports the LACP protocol. The 6500 supports both PagP and LACP to create the etherchannel. For a full list of ASA restrictions please see the following link
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...