This one has caught me out more than once. The default setting is "DCHP with failover" which means that if your switch comes up before the DHCP server (entirely feasible), it sets itself up on 192.168.88.1 and then doesn't seem to change when the DHCP server comes up. This means that you run the risk of having two devices (router & switch) on 192.168.88.1...
So what's best practise here? I'm thinking that either moving the router to 192.168.88.254 because then if you add a new switch, all that will happen is that it fights with other switches you've forgotten. Or a totally different subnet like 192.168.90.0/24?