Dhcp returns old default gateway

Hello, everybody,

I have set up a new firewall/router. The old router had the IP The new one has After the new router worked I changed the default gateway on the UCS in the network settings to

I also changed the DHCP settings accordingly:
However, all clients still get the old GW via DHCP (despite multiple reboots). What have I forgotten?

with best

the DHCP lease time

default ist most 8 days - so if its a windows client you may run ipconfig /release and ipconfig /renew which should do it