I received the same message as you did when entering this IP address in the web UI. However the IP address works fine if you enter it in the CLI. I will have to do some further research on why the web UI is behaving this way. For the time being you will need to connect to the switch CLI in order to use an IP address in this subnet.  A common used tool to make a telnet/ssh connection to the switch is putty. [URL] Once the program is open select telnet as the connection type. If telnet has been disabled and ssh enabled, then select SSH. In the host name box enter the switch IP address. Then click the open button.  Once the CLI window is open you will be presented with a prompt that says: console>, enter the following commands. console> enable console# configure console(config)# ip helper-address 100.100.100.80 dhcp Once that is done then issue the following command to ensure the command is in place. console(config)# show ip helper-address Once you are satisfied with the configuration you will need to save the running configuration to the startup configuration. console(config)# end console# copy running-config startup-config Let us know if you have any questions about this process. 
Im trying to enter the IP address of the DHCP server (100.100.100.80) but it keeps telling me it has to be in A.B.C.D format.   This is on a N2048 switch.  Basically what Im trying to do is setup DHCP relay from vlan 2 to vlan 1.  Ports 1-24 are vlan 1 and 25-48 are vlan 2  the DHCP server is physically plugged into port 1 if that matters.  
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