There is no configuration required on router2 to support this. The helper-address on router1 will see the DHCP request and send a unicast packet to 1.1.1.1. When it gets to router2, then router2 just does normal IP forwarding of the packet. router2 not know or care that the packet is a DHCP request and just does normal forwarding.
HTH
Rick
HTH
Rick
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