It’s important that the so-called SiteUrl which needs to be configured in your deployment’s config.json resolves to the Mattermost host. If you want to access the server using two different IPs for loadbalancing purposes (although I don’t know why you’d want to do this), you can create a DNS record with two IPs for your SiteUrl and that should work then. If these are two completely separate IPs and one of them f.ex. is an internal IP and you want internal clients to access it over the internal IP, then this is also possible but you need to make sure that your internal clients can resolve the value from SiteUrl properly (you might need a local hosts file entry, a DNS override or DNS doctoring on a security device in your network to achieve that).