the ip helper-address allows a router or multilayer switch to act as a DHCP relay agent.
The DHCP request message sent by clients is sent to address broadcast 255.255.255.255 and cannot be routed to another IP subnet. It can be converted by using the
command under the SVI interface or router subinterface. This enables the DHCP relay function and allows to convert the unroutable DHCP requests in routable packets with a destination that is the IP address of the remote DHCP server. The DHCP relay agent network device populates an internal field with the IP address of the router subinterface on which the original DHCP request has been received (GI address). In this way the remote DHCP server can use this info to pick up a free IP address ( if any) from the appropriate DHCP pool. The DHCP server answers to the DHCP relay agent that can send out the DHCP offer ( containing the assigned IP address) to the client.
Your router is acting as DHCP server locally so you don't need those ip helper-address commands on router subinterfaces. Also when used the ip helper-address command contains an IP address that is not the same as that of the subinterface on which it is applied but that of a remote server.
Thank you very much for that info Sir, your answers are really a big help for me beacuse i'm just a beginner and currently having my training in CCNA. if i encounter new problems I hope that it would still be welcomed.
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