70-216 - Multi-Segmented DHCP Confusion

Author

Multi-Segmented DHCP Confusion

csiszerd

2001-12-08, 9:31 pm

On a video I was watching for the 70-216 the trainer was talking about having a DHCP server on one segment (192.168.1.0 was his example) and some clients on a different segment (192.168.3.0) one hop across the router and a DHCP relay agent on this segment.
He resolved this by creating a second scope for the other segment. (In this situation they had the same DNS and WINS servers)

I think something is missing here.
How does the DHCP Server know not to give a 192.168.3.0 address on the 192.168.1.0 segment. What tells the DHCP server which segment gets which scope?

DC

Joe Blacke

2001-12-09, 11:51 am

When a Windows 2000 DHCP server receives a DHCP request BROADCAST, it can only issue a lease from the scope that includes the subnet to which the IP address of the NIC card on the server.

When using a relay agent, the request is sent as a directed packet across the router, to the DHCP server. Since it is a directed packet and not a broadcast, the DHCP server is provided the IP address of the DHCP relay agent. The DHCP server then looks for a scope that includes the subnet address of the DHCP relay agent and will issue an available address from that scope.

csiszerd

2001-12-09, 2:01 pm

I was wondering how it knew which subnet it was.
Thank you!

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