# Cisco ASA VLANs and Sub-Interfaces **URL:** https://forum.networklessons.com/t/cisco-asa-vlans-and-sub-interfaces/824 **Category:** Lessons Discussion **Created:** [December 19, 2016, 4:38pm UTC](https://forum.networklessons.com/t/cisco-asa-vlans-and-sub-interfaces/824 "2016-12-19T16:38:14Z") **Posts on this page:** 1 **Showing post:** 4
### Author: ![bill.macmillan](https://cdn-forum.networklessons.com/letter_avatar_proxy/v4/letter/b/e47c2d/32.png) [@bill.macmillan](https://forum.networklessons.com/u/bill.macmillan) #### Post date: [March 5, 2015, 4:33pm UTC](https://forum.networklessons.com/t/cisco-asa-vlans-and-sub-interfaces/824/4 "2015-03-05T16:33:26Z")
If I have an existing interface on an ASA5580 redundant pair and want to create subinterfaces on that interface are there any production challenges I will face? Let say I have Gi8/2 with an existing ip 172.21.16.254, now I want to create two subinterface on Gi8/2 one for 172.21.16.x and one for 10.248.80.x. I know how to create sub-interfaces however not sure of the impact, I know when I move 172.21.16 to a subinterface I will lose connectivity while I reconfig the interface but I am wondering if I need to reload the ASA once the config is done or will it update as I config without a reload requirement. Any other thoughts you might have. I also realize that I need to change the access switchport connection to a trunk port. --- _[View the full topic](https://forum.networklessons.com/t/cisco-asa-vlans-and-sub-interfaces/824)._