I work at a college, we recently updated our SCCM environment to current branch and we added 6 DP across the campus to server the different Colleges.  We have set up boundaries in the environment for the colleges to point to the DP in their building or to the nearest DP based on network hops.  Question is do we need to set up the IP helper in each of the different switches for those Colleges to point to those local DP's or nearest DP or should the ip helper point to the main server?  

iphelpers should point to where you intend to PXE boot from, so from the local (nearest) distribution point hosting a WDS role

Use PXE to deploy Windows over the network with Configuration Manager

Are the DPs PXE enabled? Are the DPs on the same network segment as the clients?  You only need to configure IP helper when the client is separated from the DP through a router/switch.

 

https://www.manishbangia.com/ip-helper-address-configuration-for-pxe-boot/IP HELPER-ADDRESS CONFIGURATION FOR PXE BOOT